First, a little thrust vectoring history. The USAF tested a 3D nozzle on the Multi-Axis Thrust Vectored F-16 in the early 1990s. It was found that thrust vectoring was really only useful at speeds below 250 knots (with the F-16; the speed will vary with other jets). Above that speed the jet had enough g available and was maneuverable enough that thrust vectoring didn't add anything. Also, at high speeds, if the nozzles start to swing the jet violently around you're apt to induce unacceptable loads on the airframe.

Thrust vectoring, whether 2D or 3D, is a two-edged sword. If you're going to use it, you'd better kill me now. Ever seen videos of the Super Flanker spinning around like a top and doing back flips at an airshow? First off, the jet is slow – not a place to be in a multi-bogey environment. Second, when thrust is steered off-axis the axial component of thrust is decreased. Axial thrust pushes the jet (and wing) through the air at a speed required to maintain lift. Take away forward thrust, take away speed and lift. Go back to the videos. What's happening? The Flanker is dropping like a rock at slow speed (no lift is being produced by the wing). If the Flanker pilot does not kill me now, the other edge of the sword is about to fall. He's automatically building in vertical turning room for me and it's going to take an unacceptable amount of time for him to get enough smash back to take it away due to his low airspeed. If I'm still alive I'm turning him into a strafe rag.

I flew enough BFM against the Raptor before I retired where the new Raptor pilots were discovering there's a time for thrust vectoring and there's a time to leave that club in the bag.

The delays risk adding significantly to the cost of running the existing Apache fleet, and of acquiring new aircraft direct from Boeing in the US at a cheaper price.

The dilemma of giving work to a British firm or buying a much cheaper option is much like the one that occurred back in 1995 when the current generation of attack helicopters was bought.

Then the government opted for a contract with Westland that involved fitting the basic American helicopter with new engines, defensive aids and communications taking its price from around £20m each to £44m per aircraft.

Lt Gen Gary Coward, head of the Joint Helicopter Command from 2005 to 2008, told Newsnight that the earlier Westland deal "cost an awful lot of time and an awful lot of money".

Newsnight understands that Boeing's current offer to the British government is, once again, around £20m per helicopter, which presents the Mo D with an opportunity almost unique in defence procurement history, to buy a new weapon for a fraction of the price of the one it is replacing.

Lt Gen Coward says "there really is no choice" now and that Boeing's offer "is the only sensible option".

Yet, although the Mo D made its recommendation to No 10 in October last year, stating a preference for the Boeing option, the order has been held up following representations to Downing Street by AgustaWestland.

Newsnight has been told that the order cannot go ahead until "after the election" because of the political sensitivities of opting for an off-the-shelf buy from Boeing.

Former defence secretary Geoff Hoon, who now runs Agusta Westland's international business division, has been part of the lobbying effort.

The delays though could be very expensive. American suppliers will cease supporting of the equipment carried in the Army's current generation of WAH-64 Apaches in 2017, adding greatly to the costs of maintaining the existing fleet.

And Boeing's offer price to the UK is conditional on it joining an imminent, much larger, order for the US Army, giving economies of scale.

Even if an order were placed immediately after the election, the aircraft would not enter service before 2020. The Army fears a "capability gap" and rising costs as support for the existing plane is switched off from 2017 onwards.

The BBC understands that AgustaWestland has persuaded the government that it should be allowed to make a new bid for the business.

Many in the Mo D fear that will provide an opportunity for more "gold plating", increasing the value of the work to the Yeovil-based manufacturer, of the kind that happened with the WAH-64.

Buying into direct into Boeing's project, called Block III Apache AH-64E, a batch of 240 machines for the US and other armies, offers significant economies of scale.

However it would leave AgustaWestland short of work, and backers of the firm argue that even the so-called "Vanilla", or off-the-shelf, Boeing helicopter would need some modification, for example to its communications equipment, to make it interoperable with British forces.

In addition, the Mo D is so keen on the Boeing option that it has already discussed with the Pentagon, ways in which the Block III Apache order book might be kept open a little longer so that the UK can join.

The Mo D said in a statement: "The assessment phase of the Attack Helicopter Capability Sustainment Programme, which will supply 50 latest generation Apache helicopters to the UK, is ongoing.

"This phase includes establishing best value-for-money for the taxpayer and will conclude in March 2016, at which point a decision will be made as to the best procurement route."

However, the suggestion that the assessment will finish in March 2016 marks yet a further six-month delay to the project because Newsnight understands that the Joint Helicopter Command was determined to reach that milestone by September 2015.

Awarding the new contract offers the Mo D a chance to make a landmark decision to put cost-effectiveness ahead of industrial interests. But the politics involved with the West Country helicopter making business have never been easy, as previous defence secretaries can bear witness.

New small diameter bomb doesn’t fit inside Marines' F-35B

Joint Strike Fighter engineers will have to make adjustments to the weapons bay of the Marine Corps variant of the F-35 so the aircraft can carry a pin point glide bomb by 2022, JSF program officials said.

The Small Diameter Bomb II, or SDB II, can acquire and track moving targets from distances up to 40 miles and is slated to enter service by 2017. However, while the weapon can be integrated into the Air Force's F-35A variant, the new weapon cannot fit into the current configuration of the Corps' F-35B short-take-off-and-landing variant of the JSF, F-35 program officials acknowledged.

JSF officials said the SDB II was not intended to integrate onto the Marine Corps variant before 2022 and therefore "not an issue or problem." However, the changes will require modifications to the internal weapons bay before it can be integrated.

The JSF program says the program is waiting to make these modifications because the SDB II is a developmental weapon and there may be other adjustments needed to the internal weapons bay to accommodate other future weapons, JSF officials explained.

The SDB II is not intended to deploy on the F-35B when it reaches operational status later this year. The software configuration onboard the F-35B will not be able to fire the SDB II until 2022, JSF officials said.

JSF officials could not say how much the modifications to the internal weapons bay of the F-35B will cost because they are still being determined and not slated to begin for several years.

The Small Diameter Bomb II represents a technological departure from other precision-guided air-dropped weapons because of its ability to track and hit moving targets from long distances.

The Pentagon has already invested more than $700 million into SBD II development.

A key part of the SDB II is a technology called a "tri-mode" seeker - a guidance system which can direct the weapon using millimeter wave radar, uncooled imaging infrared guidance and semi-active laser technology.

Meanwhile, the Air Force's F-35A Joint Strike Fighter variant is making progress with its weapons separations testing, Air Force officials said.

"We've had a busy year in terms of looking at doing testing for weapons separation," Lt. Gen. Ellen Pawlikowski, military deputy for Air Force acquisition, said.

Since last year the Air Force has had four different AIM-120 tests as well as a few Small Diameter Bomb separation tests and some JDAM tests, she added.

Pawlikowski said weapons preparation is on track for the Marine Corps short-take-off-and-Landing F-35B variant as well, adding that it is slated to reach operational status, called initial operating capability or IOC, by this summer.

"The weapons preparation is on track to support the Marine Corps and Air Force IO Cs," she added.

Meanwhile, in November of last year, the Joint Strike Fighter completed three live-fire weapons delivery accuracy tests involving two AIM-120 Advanced Medium Range Air-to-Air Missile, or AMRAA Ms and one Joint Direct Attack Munition, or JDAM.

"These events included the first supersonic-guided missile launch and the first JDAM release on target coordinates generated from the Electro-Optical Targeting System," a JSF program office statement said.

The F-35 can carry more than 35-hundred pounds of ordinance in low observable or stealth mode and over 18-thousand pounds uncontested.

There are 11 weapons stations built onto the F-35 airframe; four of them, weapons stations four, five, seven and eight are internal weapons stationed engineered to allow the aircraft fly and drop weapons while in stealth mode, JSF officials said.

However, there is an exhaustive separation process and extensive evaluations involving testing weapons "drops" before weapons are live-fire tested against targets, Pentagon JSF officials said.

"We take a crawl, walk, run approach to weapons testing where we will begin by putting a weapon in a weapons bay and dropping it on land onto some padding. Then, they will test the weapon flying to see if it releases and drops safely. Then you connect to the last stage and test whether the weapon can find the target," said Joe Della Vedova, JSF spokesman.

F-35 weapons separation testing has also involved the GBU-39 Small Diameter Bomb, Paveway IV missiles and external "flutter tests" with the AIM-132 Advanced Short Range Air-to-Air Missile.

Overall, the Air Force plans to buy 1,763 JSF F-35A multi-role fighters.

In January of this year, the Air Force stood up a special F-35 integration office to ensure that all aspects of the platform are properly developed, Pawlikowski added.

She added that some of the technologies, such as intelligence, reconnaissance and surveillance ability, or ISR, and increased sensing capacity on the F-35 might lead the Air Force to develop new concepts of operation, tactics and procedures for the platform.

"I don't know that we have a full appreciation of everything we are going to be able to do with the F-35 until we start to actually use it," Pawlikowski said.