Every movie that is very successful pays attention to detail. That doesn't necessarily mean that the movie is big budget. There are a lot of high-budget movies that don't do well because the cast and crew are not dedicated to the details. In Airplane though, the actors committed and put in more time than their contracts required.
Yes, the fact that the actors in Airplane created their own dialect to use in the movie is a testament to this film's greatness and ability to inspire creativity. The actors in this move were so taken in by its plot that they decided to use their admiration for the film as an inspiration to create.
Airplane is a great movie because everyone worked so hard on it. The actors could have used the language that was written for them and come off as slightly racists, but because they worked so hard on that small part it ended up being timeless and much more entertaining than it could have been.
There are a lot of movies out there that have actors winging their lines a little bit in the name of genuine expressions. However, almost none of them rise to the level of 'Airplane' because of the immense talent that the cast had. Leslie Nielsen played the perfect straight man in this movie, and the comedy all revolves around his wonderful talent for such roles.