... it was a winged creature: if bird, then greater than all other birds, and it was naked, and neither quill nor feather did it bear, and its vast pinions were as webs of hide between horned fingers; and it stank. A creature of an older world, maybe it was...
Large flying creatures are a staple of Fantastic Fiction. This trope comes in a few distinct flavors:
Most Giant Flyers are simply large aerial predators who swoop down on our heroes from above. Generally, the Flying Predator version isn't outright evil.
Some Giant Flyers actually are recruits of the Big Bad. In The Tough Guide To Fantasyland, Diana Wynne Jones calls this variety "Leathery Winged Avians" (never mind the fact that many of them are feathery winged).
Giant Flyers can also be Big Damn Heroes. As mentioned in Horse of a Different Color, an animal that can fly and be ridden on is probably the most-desired fantasy mount. Where such Giant Flyers appear, expect there to be at least one scene where they must swoop down to rescue a non-flying character who has fallen from a great height. Such scenes in The Lord of the Rings earned this subtype the name "Deus ex Machina Airlines" from the Harvard Lampoon parody Bored of the Rings.
Note that Giant Flyers can be either literally gigantic or just relatively large compared to the other characters. Compare Our Dragons Are Different, Dragon Rider, Winged Humanoid, Space Whale, Feathered Fiend, Ptero Soarer, Living Gasbag and Living Ship. See also Giant Swimmers.
In Real Life, the largest flying birds are limited by the manner in which avian flight feathers grow and historically have never been much bigger than even modern Condors (wingspan about 3.5m) with the exception of Argentavis (wingspan perhaps up to 7m). Pterosaurs evolved to be much larger, but then anything bigger than a quetzalcoatlus (wingspan about 10m) is running up against the Square/Cube Law — it gets really difficult to take off, since the wings become too heavy to overcome their own weight, let alone the rest of the body. The largest bird species generally spend most of their flight time gliding rather than flying, and prefer to land on a high point rather than the ground, as they tend to need a downward dive at the beginning of a flight to build up momentum. In fiction, if any effort is made at all to explain why an overly large flying creature can exist, the go-to explanations are low-gravity planets and magic.
Yu Gi Oh Slifer The Sky Dragon, The Winged Dragon of Ra, and many others.
Lots and lots of these in Digimon. Often times it's someone's partner Digimon (such as ShineGreymon), though there are a few notable exceptions (such as Azulongmon).
The Mass-Production EVAs from End Of Evangelion. Picture a bone-white humanoid vulture with a 200-foot wingspan, no eyes, a permanantly-grinning mouth with incongruous red lips and bad teeth, and you may end up like Shinji or Asuka.
These exist in Hunter × Hunter. There a scene in both Anime and Manga where it cuts to Ging, sitting on the back of giant frog. It pans out, and it shows that giant frog is on the back of a giant dragon, which takes off and flies off into the distance.
In Naruto, there is the Seven-Tailed Demon Beetle, a cross between a 6-winged dragonfly (plus tail) and an armored rhinoceros beetle.
Flying-type Pokemon that can evolve will usually end up being (relatively) large in their final stages.
James Cameron's Avatar has two main kinds of giant flying predator: the Banshees (or Ikran), which are dragon-like, four-eyed and four-winged blue creatures often mounted by the Na'vi; and the very rare Great Leonopteryx (or Toruk), a similar species, only even bigger and red, that only the most badass Na'vi have ever been able to ride.
More specifically, banshees have a wingspan of 13.9 meters while the "Leo" is at least 25 meters. The size of those creatures is deceptive because the Na'vi riding them are 3 meters tall.
Wayne Barlowe's Expedition, and the Speculative Documentary based on it, Alien Planet, feature the jet-propelled, lance-headed Skewer, which has a 60-foot wingspan. The book also mentions the Ebony Blisterwing, which is said to have a wingspan of up to 1000 feet.
The Seanchan of The Wheel of Time have scouts that ride giant winged creatures called raken and even larger to'raken as mounts.
To'raken even carry boxes of ten or twenty elite soldiers called Fists of Heaven, which they use for aerial assaults. If they put damane (slave mages) in the transport boxes, they can even be aerial artillery.
Worsel the Velantian in EE Doc Smith's Galactic Patrol. Our heroes are being dragged by savage other-wordly beasts to a cave in which they will meet their doom when Worsel, a thirty-foot-long sentient flying reptile, drops from the sky and scatters the beasts in a shower of body parts.
J.R.R. Tolkien's fell beasts, Eagles, and Uruloki dragons. The crebain, used by Saruman as spies, were not giant, but were larger than normal crows.
The tarns of Gor are a well thought out example. Despite having a 30 foot (9 meter) wing span they are so light that two strong men can easily lift one above their heads.
The dragons of the Malazan Book Of The Fallen are immense. Most natural dragons have already died out by the time of the main story, but Eleint Soletaken still have the ability to transform into the massive beasts. It is noted that the Soletaken often rely on sorcery to remain airborne, especially if their wings are damaged.
Dragons of the Inheritance Cycle literally never stop growing. They're typically born from eggs roughly a foot long and within a few weeks are large enough to ride, and nothing is ever said to indicate that that remarkable growth rate declines. As of Brisingr, less than two years after she hatched, Saphira was so large that jumping down from her back when she is standing up is a long enough drop to either sprain or break bones, and particularly old dragons (before they were wiped out) were said to be mistaken for hills at a distance.
Many of Visser Three's giant morphs in Animorphs fall into this category.
The Known Space short story "Safe at Any Speed" features the Roc, a gigantic alien bird large enough to swallow a car.
Live Action TV
Torchwood has its own pet pterosaur cum watch-flyer called Myfanwy.
Subverted by Primeval, in S1 in which the Pteranodon is explicitly stated to be a fish-eater and achieves no casualties other than an accidental injury, and the Monster of the Week is actually a swarm of smaller, flying pterosaurs who prefer Death of a Thousand Cuts to carrying the food off.
Played straight in S3 with the giant praying mantis from the future.
Doctor Who had a giant (as in the size of a carthorse) wasp in the episode "The Unicorn and the Wasp".
Skywhales and Kites in Blue Moon.
The Red Dragon Thunderzord and platform in Mighty Morphin' Power Rangers season two. Besides the Fire Bird Thunderzord (which, as a fairly traditional aircraft doesn't count for this trope), the rest of Thunderzords could at least hover.
In The Outer Limits revival episode "Tempests" the gas giant Leviathan's atmosphere harbored two giant flyers: "pteranodons," gigantic winged predators that had only been seen on "deep radar" (the characters encounter a skeleton) and "baleens," kilometer-sized jellyfish-blobs that float through the clouds and have dog-sized Giant Spiders in their guts, either as parasites or symbiotic organisms.
The flying werepanther that Freya turned into in Merlin
A whole flock of man-eating pterosaurs menaces Terra Nova.
More than a few flying dragons get cast in this role; Wyverns, in particular, swoop down on many a hero in folklore.
The Suckers from Diablo II are small compared to some of the entries on this page... but are still weird mosquito-things as big as a large man.
Skies Of Arcadia has several, with most of them serving as ship bosses. Four of the six biological superweapons known as Gigas can fly, and you can also optionally fight a Roc, a flying kraken, a giant... flying... spider thing, and an enormous Looper.
Demon's Souls features the Storm King as the boss at the Isle of the Shadowmen. A huge leathery-winged thing the size of Texas. It also comes accompanied by a fleet of Storm Beasts, smaller versions of itself that are more than twice as big as the player-character.
Dragon Age: Origins contains a really nasty High Dragon that a group of people have decide is the reincarnation of the Prophetess Andraste. You don't have to fight it, but the cutscene upon entering the mountaintop area suggests that it falls into this category.
Dragon Age II has another High Dragon as a Bonus Boss near the end. This one just wandered into an inhabited area, no crazy dragon-worshiping cults this time around.
The Archdemon. This presents a bit of a problem for the heroes, as the Blight can only be ended with the Archdemon's death, but it's ability to fly allows it to easily stay out of the Gray Warden's reach. Luckily, Riordan manages to sneak up on it and force it to land by slicing one of it's wings open.
The Roc colossus in Shadow of the Colossus falls into this category as it does actively attack you, whereas the Serpent pictured above simply flies around.
To be fair, it only attacks you after you shoot at it with arrows. Otherwise it just watches you from its perch.
Though the serpent pictured above simply flies around, thank goodness it doesn't attack. According to the Word Of God in the artbook, the sucker is the longest (largest?) colossus, measuring in at about 200 meters (for non-metric folks, that's a whooping 656 ft.) The evidence is here, though in Japanese.
The campaign mode of the sequel has the Leviathan, which is somewhere between thirty to fifty times the size of a battlecruiser. Even though the game's units aren't to scale, it's clearly meant to be enormous.
Dwarf Fortress has Giant Eagles, which is kind of a misnomer since there aren't any normal-sized eagle in the game. And then there are rocs, which are the third largest creatures in the game behind fully-grown dragons (which take fifty times as long to reach their full size) and giant sperm whales. A newly-hatched roc is as big as a fully-grown giant eagle.
The Mountain Roc in Golden Sun: Dark Dawn, which is a) large enough to carry off human prey when Amiti recalls indirectly encountering it as a child, b) large enough that the nation of Morgal worships it as a god, c) large enough to force the camera to zoom out during your boss fight against the damn thing (and you still don't get the whole thing on your screen), and d) large enough that its gizzard acts as a Womb Level, albeit a short one.
Lampshaded in Final Fantasy X by Tidus in the desert around Home, where a giant bird enemy is a frequent monster.
How can a bird grow so big?
The eagle in Angry Birds, which will wipe out all the pigs in a level.
The main antagonists of The Elder Scrolls V Skyrim are large, ANGRY dragons. Much of the time spent fighting them will be trying to get away from them when they're in the air raining fire down on all the things.
A huge number of the monsters in the Monster Hunter series are of this nature, the two most recognizable ones being the Rathalos and Rathian. They seldom spend much time flying at a height where you can't reach them, generally only doing it when they're moving between areas or for specific attacks. Otherwise, they're usually seen moving about on foot or with a low hover.
World 5-SHIP: Eagle Path in Super Mario Fusion Revival. Based on the 4th stage of Golden Axe, "The Fiends' Path", this level takes place on the back of a giant eagle. Dangers include homing feathers, large Mana Beasts, and unstable platforms.
Lord Dragon, Glaserwyrm, and Draco, from the Global Guardians PBEM Universe, were all honest-to-God dragons. Glaserwyrm was simply a monster to be beaten down. Lord Dragon was a dragon who turned into a man to act like a superhero, while Draco was a man who turned into a full-blown dragon and fought crime as a superhero.
Flying plant creatures(!) called "Swoopers" in the Star Trek The Animated Series episode "The Infinite Vulcan". There are also Flyers in other episodes (such as "The Eye of the Beholder") who are said to be different species but use the same character models.
Examples of Leathery Winged Avians
The "Birds of the Master" in the Valerian album named after them.
Abyssgreymon from Transcendence: Digital Curse is a Super Ultimate digimon who is about the same size as a Sovereign. He is forced into servitude by the first villain of the series.
The Fell Beasts used as mounts by the Ringwraiths in The Lord of the Rings. While they are more vaguely described in the books, here they are portrayed as large, leathery-winged and scaled, with two legs, long necks and blunt, snakelike heads. They are used by the Ringwaiths almost like reconnaissance planes while patrolling the lands around Mordor, but are taken directly into battle at Osgiliath, Mina Tirith and The Black Gate.
The Zlanbeasts and Kraan from the Lone Wolf series; ugly reptilian creatures with leathery wings serving the Darklords as flying mounts from them and their various troops. The Grand Master series also features the Lavas, dragon-like monsters in direct service of the god Naar.
Flying monkeys from The Wonderful Wizard of Oz. Though it should be mentioned that, in the book, the Monkeys are merely flying predators who were enslaved by the Wicked Witch of the West via a magic hat which may be used to summon the monkeys three times. Dorothy gains the rights to this hat after killing the Witch, and the Monkeys aid her and her friends three times. Dorothy then handed the hat off to the Good Witch of the South, who declared she would use her three to get Dorothy's friends back home. She then gives the hat to the King of the Monkeys so no one else could use it, effectively freeing the monkeys.
The Rooks controlled by the Dark in The Dark Is Rising straddle the line between this and the flying predator subtrope.
In Guards! Guards!, mention is made several times of the fact that 'noble' (ie, giant and mythical) dragons are, intrinsically, wrong; nothing that big with that wingspan should ever be able to fly - Sybil even mentions the thing about how you can't just scale something up and expect it to work. The only way they can survive in the real world is by, essentially, feeding on magic. Lots of it. And that doesn't go so well.
The original Gwythaints of The Chronicles of Prydain are almost a subversion. They used to be good; they were peaceful flying creatures akin to real-life Condors. Somehow, they were corrupted by Arawn — but there is still good in them. Taran rescues a young Gwythaint who later goes on to rescue him.
The Ak-Baba from Deltora Quest were monstrous flying servants to the Big Bad. They scattered the jewels of Deltora across the land and terrorized the heroes on more then one occasion.
In the book Dark Lord Of Derkholm by Diana Wynne Jones, the titular character (and protagonist) is supposed to have a supply of Leathery Winged Avians on hand. What he actually ends up using are a flock of rather snarky intelligent geese.
The byakhee from HP Lovecraft's "The Festival", and the night-gaunts from The Dream-Quest Of Unknown Kadath.
Many of Visser Three's giant morphs in Animorphs fall into this category.
The Star Wars Expanded Universe states that among the many species that went extinct when Alderaan exploded were a number of massive flying creatures called thrantas, they were used as beasts of burden. Fortunately one species was exported to Bespin, which has an entire airborne ecosystem.
Live Action TV
Stargate SG-1 once faced a dragon, in their final season. Vala named it Darryl.
The series finale of Angel had Angel going to fight a large dragon once the city goes to hell. By the beginning of After the Fall he has become Angel's ally.
The Tyranid Harridan in Warhammer 40000. A huge winged monstrosity with razor sharp claws, pointy teeth and acid-shooting "bio cannons". Often carries around flocks of Gargoyles, smaller flying Tyranids.
Quite a few other varieties of Tyranid come in winged strains, and then there are most of Tzeentch's demons...
A lot of Warhammer Fantasy Battles armies have access to one or more of these.
In the Iron Kingdoms world, any of the spawn of Ever blight that happen to have wings. They all have chitinous plates where their eyes should be, but make up for it by having an prodigious number of sharp teeth, as well as a variety of other natural weapons such as claws and blight-breath. The Angelius has itself no less than six wings. And then they are further topped by Archangels.
In Dragon Dice, all races have access to the eponymous dragons by summoning them through magic. Most races have some form of flying cavalry or monster in addition to having access to dragons.
Ridley in Metroid, although he's not really a servant of the Mother Brain (he's the leader of the Space Pirate army who ally with the Mother Brain).
El Goonish Shive has the Bulldog Dragon. It's basically what you'd get if you combined a bulldog, a bat, and a goat while making it the size of a small car and reptilian.
In Code Lyoko, the Frelions and flying Mantas are XANA's aerial fight force. The Frelions are Goddamned Bats of the swarm kind, and the Mantas are occasionally used as steeds (most notably William's Black Manta).
Examples of Deus Ex Machina Airlines
Anime & Manga
Birdramon from Digimon Adventure was ridiculously large compared to the rest of the cast; large enough that several of the chosen could ride on her feet. Other Giant Flyers include Zhuqiaomon from Digimon Tamers, Qinglongmon from Digimon Aventure 02, and Imperialdramon. Imperialdramon, furthermore, had two different forms: one was humanoid and used mainly for combat (called "Fighter Mode"), while the other was a quadruped with a domed glass-like shield on its back which it could carry passengers in.
Many (if not all) of the dragonets that appear in the Manga / AnimeNaru Taru can fly and carry their owners with (or even inside) them.
The giant hawks flown by the Chosen Eight in ElfQuest.
Several comic book characters ride flying horses; Valkyrie, Black Knight, Dreadknight, Shining Knight, basically a lot of knights.
George does a pegasus and a dragon in With Strings Attached, always acting as a Deus Ex Machina Airline for Ringo and, usually, someone else (As'taris and the Hunter). Of course, he becomes many smaller kinds of flyers as well.
Sacredgreymon drives Abyssgreymon from Digital City near the end of Transcendence: Digital Curse.
The Land Before TimeVII features a Giant Flyer (really as that's what Pterosaurs are called in this verse) who was able to transport all of the characters off the top of a volcano just before it erupts. Certainly, there were some impressive Pterosaurs in real life. Not sure if we buy one giving a young sauropod a ride.
The Itikars, giant birds used as steeds by the Vassagonians in the Lone Wolf series. Lone Wolf also "borrows" a Zlanbeast on a few occasions to travel through enemy territory.
The Nac Mac Feegle in the Discworld, who have two things going for them: (i), they can tame any bird species and use it for steered flight; and (ii), they have the secret of the "crawstep", an ability to instantaneously translocate between locations and dimensions. In Snuff, this is used to bypass the inconvenient truth that normal travel between Ankh-Morpork and Howondaland would take weeks. A Feegle can fly there in mere hours using the crawstep.
The Gars in The Sword of Truth series. They're only about man-sized, and can only seem to carry skinny teenage girls, or wizards using magic to make themselves lighter.
Another Garth Nix example: in Shade's Children, "Wingers" are leather-winged flying beasts. Technically, that would put them in the category directly above, but as Shade notes, the normal laws physics makes it impossible for them to fly, but the Change Reactors make it possible.
The Dirigible Behemothaurs from Iain M. Banks' Look to Windward are giant flyers of a sort, though very large (large enough to provide living space for dozens of human-shaped creatures in their various nooks and crannies) and rather slow and inscrutable. You generally wouldn't chat to them, certainly.
The night-gaunts in Brian Lumley's Hero of Dreams series. Yep, they've switched sides since Lovecraft's day (see above).
The Caterbird from the Edge Chronicles always shows up at the exact right time. In fact, it promises to do so as soon as it's introduced.
Tobias has been this in Animorphs when the others are in insect morph. Other times they just morph birds themselves.
The Roving Reptilian Rescuers in The 13 1/2 Lives of Captain Bluebear, including the aptly named Deus X (Mac) Machina.
John Varley's Titan series features sentient blimps. A species of symbiotes lives inside their "stomachs" and helps them out by bringing in vegetable matter for the blimps to digest. Blimps are pretty laid-back and it's possible to convince one to give you a ride, as long as you're not carrying fire or any means of making fire, which they're scared to death of for good reason... they get around the square-cube law by internally producing hydrogen so they're lighter than air (but also rather explosively flammable).
Live Action TV
Kilgharrah in the series 2 finale of Merlin carries Merlin back to Camelot.
Parodied in The Halfblood Chronicles. One of the heroic Dragons gives a ride to a character who has just joined with the heroes. They both come away from the experience saying that it had to be the most uncomfortable way to travel imaginable.
Pokémon has an amusing application of this trope in the form of the teachable move "Fly". Any Pokémon who can learn it effectively becomes your Deus Ex Machina Airline. (In practice, this means you are able to revisit important locations within the game.) The list of characters who can carry you while flying includes everything from creatures who fit the Giant Flyer trope, like the big, Bad Ass dragon Salamence. But it also hilariously includes tiny little Zubat and (possibly the most amusing) Doduo◊, a two-headed flightless bird thing without wings. Generally the entire evolutionary lines of common bird Pokémon (Pidgey, Hoothoot, etc.) can learn Fly even in their small initial forms (for one thing, Pidgey's Pokédex entry calls it a Tiny Bird Pokémon). Natu stands out as a rare example of a common bird Pokémon that can't (like Pidgey, it is also described as a Tiny Bird Pokémon), though its evolved form, Xatu, can.
Much more amusing than Doduo is Smeargle. They aren't bird-like or winged at all (they're dogs), but that doesn't stop them from sketching and using Fly.
Best of all for a Deus Ex Machina Airline? A legendary like Rayquaza, Moltres, or Ho-Oh. You are riding a friggin' phoenix, or the Ziz itself.
This is even funnier if you have a Golurk and teach it Fly. It's a possessed golem about twice the size of the player, and many fans depict it with a built-in jetpack.
Many an episode of The Flintstones has the characters flying on airplanes mounted on giant pterodactyls, as well as planes with smaller pterodactyls as engines.
Rune Factory Frontier has a whale shaped island that you can use a beanstalk to climb onto. This island is intelligent and needs your help to defeat the infestation of monsters inhabiting the very large dungeon inside of itself.
Fluzzard from Super Mario Galaxy 2, which is a giant parrot in which Mario must ride on in the "Wild Glide" and "Fleet Glide Galaxies" to obtain their Power Stars, and later on he must use him to race a team of hummingbirds.
Discworld example: Constable Buggy Swires of the City Watch; a gnome who maintains a squad of (semi)trained pigeons (and a turkey vulture in Monstrous Regiment).
Predating Buggy Swires is The Death of Rats riding Quoth the Raven and the (semi)trained pigeons (see Soul Music which happens two years before Jingo).
One of the Nac Mac Feegle in The Wee Free Men has a trained Sparrowhawk whom he rides around on. This is probably a direct parody of...
... the titular characters in The Minnipins. They're tiny gnomes who ride upon birds. Of course, they happen to know a huge Mute Swan who can carry their new human friend.
Long before he wrote it into Discworld, Pratchett gave geese to the Floridian Nomes in Wings, the last part of the Nomes Trilogy.
Gnomes in the Gnomes and Secrets of the Gnomes illustrated books hopped a lift on large birds quite often. One slightly Narmy illustration shows a pair of gnome newlyweds being carried off to their honeymoon by a swan.
Tamora Pierce can go here because hers are varied and hard to categorize. She has traditional dragons and griffins; kudarung, which are traditional winged horses except that they come in widely varied sizes, making some of them Pocket-sized Flyers; hurroks, clawed, predatory "horse-hawks" with batlike wings; and Stormwings, which are half human, half giant sharp-metal-feathered bird, and aren't evil but do take natural pleasure in human suffering. They're all immortal unless killed (except possibly the kudarung, which aren't specifically identified as immortals and might not be, since they didn't enter the human world under the same circumstances as the immortals we know).
In Stephen Baxter's book Evolution, he invents a species of pterosaur dubbed the "air whale" with wings a hundred metres across. Living off tiny creatures in the stratosphere, it had paper thin hollow bones. They mated on the highest mountain peaks and it is suggested there are very few of them due to the lack of food. Able to circumnavigate the globe with the aid of wind currents, it need never touch the ground.
All of the above are very, very possible in Spore, due to the existence of Epic Creatures. Flying epic creatures in particular are somewhat more deadly than regular ones, especially ones with higher levels of flight, because they can move much more silently and quickly than normal ones.
In the skies of the Shadow World of Age of Wonders: Shadow Magic swim whale-like Skwahl. They aren't present (at least in the official ruleset), but the description of floating Forceship unit says Syron make them from hollowed carcasses of old Skwahl.
Quake II has the Hornet (aka Flying Guardian), a hovering insectoid cyborg thing.
Half-Life has huge manta ray-like alien fliers who at some points in the game drop alien grunts. In Opposing Force, they appear right at the beginning when they start shooting down Osprey troop carriers with their lightning rays.
Perca (Priscila S. Piccin) uses large flying creatures in multiple of her comics including a giant space whale in Killer of Monsters, a flying Whale in the OCBZ Highway with a man riding it called pedro, and a similar whale (plus pedro) in Boobtrap.
Lampshaded in The Order of the Stick#754. When the large-bellied, small-winged dragon ruler of The Empire of Blood decides to fly to a royal parade, a dumbstruck Vaarsuvius remarkes that he should avoid casting magic for the rest of the day, "if only to give the laws of physics time to cry alone in the corner."
The species of Pterosaur known as Quetzalcoatlus (where "quetzalcoatl" is Aztec for "feathered snake" and was the name of a major god) had a wingspan of 12 metres and was pretty damn tall (see the wikipedia article).
The most commonly adapted Pterosaur, Pteranodon, was also pretty large as well, with an average wingspan of 7-10 metres (not quite as big as Quetzalcoatlus but still).
New evidence give possible suggestion that Quetzalcoatlus was in fact too massive to fly, but this is not well accepted among mainstream pterosaur workers.
Another extinct animal: the Giant Teratorn (Argentavis) had a smaller wingspan of up to 8 metres, but was the largest flying bird of all time.
Similarly, we have the little-known pseudotooth birds, seabirds on steroids that had bony teeth on their beaks. The largest, Osteodontornis, capped at a 20ft wingspan. Scientists speculate that it behaved like a modern-day frigatebird (basically the meanest bird on the open seas) and had a throat pouch like a pelican (basically the meanest bird on the beach). Now imagine a beach full of those things. Happy picnicking!
For a more recently extinct animal, one that humans probably did interact with, there's always the Haast's Eagle of New Zealand, at about 3 meters. They hunted moa, which ranged up to 15 times their weight (and are also bigger than humans), and lived up until a few hundred years ago.
It has been noted that, based on puncture marks found on moa pelvises, the Haast's Eagle was probably a fairly specialized hunter of the same. Moa were big, feathered bipeds. The earliest Maori colonists were most likely wearing feather cloaks same as they do now. This might have caused... issues.
The still living Wandering Albatross has to settle for a mere 3.7 metres (12 feet) at the most.
Which is pretty big, and the Albatross has to launch itself off cliffs to get into the air because it's too heavy to take off.
Some flying foxes can grow to have wingspans of 1.7 meters.
Still speculative but have been theorized that in planets with more gravity than Earth the flying creatures would be bigger, that's because a thicker atmosphere would have more oxygen and provide more lift with less area. In the other case planets with less gravity than Earth would have a thinner atmosphere and be less prone to big flying creatures.
Thinner atmosphere might result in a creature with a proportionally higher wing surface area in relation to body size, e.g. a robin with albatross wings.
Gravity does not have to be linked directly to atmosphere. Venus for instance has a much thicker atmosphere than the Earth, while being a tad smaller and having 90% of Earth's gravity. A higher gravity in itself would probably cause flying animals to become smaller.