I think I might have seen Carry On Luggage. Barbara Windsor as the air hostess, Jim Dale as the hapless co-pilot, Sid James a troublesome passenger (married to Hattie Jacques), and Charles Hawtry as the steward getting quietly sloshed as the flight goes on. Kenneth Williams is the aero engineer trying to convince the pilot that he needed to land the plane before it suffered a critical failure from a design flaw. Oh, hold on, that's No Highway, isn't it?