By which I mean is still funny, and has a minimal amount of jokes which aged poorly (not stuff that aged poorly from stuff they couldn't have known about, such as a joke about someone dying in a certain way, but then someone later died in a similar way, but aged poorly due to how problematic they are).
Bonus points for tricking Slim Pickens into thinking he was making a serious war movie, hiding every other part of the production from him.
How did they convince him that the movie where he sits on top of a bomb, waving his hat like it's a rodeo is a serious movie?
Kubrick butted heads with George C. Scott throughout the production; Scott wanted to play everything straight while Kubrick wanted more humour. Kubrick tricked Scott by getting him to perform over-the-top takes, which he said would not be used in the final film, as warm-up practice takes. Many of these takes ended up in the final cut, leaving Scott feeling angry and betrayed, and swearing never to work with Kubrick again (he came around later and admitted they made for a better movie).
Kubrick no doubt pulled similiar tricks with the bomber crew to get the shots he needed.