In Spaceballs the point of Dark Helmet and the rest of the Spaceballs is to steal air from Planet Druidia and save Planet Spaceball. They fail. And the president was trying to keep the problem hush-hush. Did the innocent residents of Planet Spaceball figure it out and save themselves, or did they perish from slow asphyxiation?
Actually, the people of Planet Spaceball knew. In fact, the news was questioning the president about it during the "peri-air" scene. So the people of Planet Spaceball know and so does the news. Eventually the people are going to get tired of hearing "we have enough air" when they obviously don't. Seeing how the Spaceballs reacted at a ship going down, it's easy to guess that as many as possible are going to try to flee the planet. When escape ships run out or the president locks the planet down, the remaining people are probably going to kill each other over the remaining air. Then the survivors will start to suffocate. That is, unless the Spaceballs manage to steal all of another planet's air, which then opens a whole new can of worms.
So how did whoever put the "out of order" sign on the self destruct cancellation button know it was out of order? There wouldn't be any reason to press it unless the self destruct was activated, and if it didn't work that time, then there shouldn't be a ship around in the first place. (Yes, yes, Rule of Funny.. I know...)
Something doesn't have to break while being used to be marked as out of order. The button may have never have been hooked up, may have been down for scheduled maintenance or simply failed a test use with a simulated destruct sequence.
The film actually completely negates its entire premise. The Spaceballs are running out of air and need to steal Druidia's supply. But when Barf, Dot, and Vespa are climbing between ships through outer space, they can breathe just fine.
Druidia had the best air. That's why they canned and exported it, and why the Spaceballs wanted it for themselves.
That's a good point - after all, that desert planet had plenty of air they could have sucked up instead.
Dot, of course, doesn't need to breathe, being a robot. Good point about Barf and Vespa, though.
Which leads to the Alternate Character Interpretation that the Druidians are intentionally letting an entire race believe they are about to suffocate at any given time simply so they can keep exporting their air and keep bringing in the money.
Why is a Druish princess singing a spiritual about Jesus?