On one of last nights reruns, Jerry was sitting in first class with a blonde model, while Elaine was in the cheap seats getting served an unwanted kosher meal. At the end, the stewardess explains to Jerry and the blonde that they had problems with someone trying to get into first class without a ticket.
Jerry said that the curtain between first class and economy was not secure, it couldn't be locked to keep intruders out. Just like the doors to the cockpits on those doomed jet planes on September 11!
MsLiz