From The Hollywood Reporter:
Arguably the best role was that of Dr. Rumack, played by the guy no one wanted or ever suspected would be funny, much less go on to have a second career starring in feature films as a goofball comic. Leslie was great in the role because he never "winked" -- let on that he knew he was in a comedy. This was essential to the style, and Leslie had a natural instinct for it.One of my all-time favorite exchanges in film:
Rumack: Captain, how soon can you land?
Captain Oveur: I can't tell.
Rumack: You can tell me. I'm a doctor.
Captain Oveur: No. I mean I'm just not sure.
Rumack: Well, can't you take a guess?
Captain Oveur: Well, not for another two hours.
Rumack: You can't take a guess for another two hours?