Here's an old one on the pilotless aircraft that I stumbled across on a Flying Jokes site:
Back in the 1970s, automation was creeping into many of the systems associated with large airliners. One day after the boffins and engineers had laboured mightily for many weeks, a fully-loaded Convair 880 took off from Heathrow bound for New York. The cabin crew did the normal safety demonstration and the aircraft taxied out to the active runway, lined up and took off in the usual manner. As the Convair climbed through about 26,000 feet, an announcement came from the flight-deck:-
"Ladies and Gentlemen, welcome onboard this the first fully-automated transatlantic flight from London to New York. So advanced are the automatic systems onboard this specially-equipped Convair 880, there is no actual flight crew onboard in the flight-deck, the door to which is therefore locked. The entire flight-plan, with all imaginable contingencies, has been programmed into quadruplicated flight management computers, all backup systems are duplicated and there is a fifth, entirely separate set of automatic systems in case of any unforeseen problems. So relax, sit back, enjoy the cabin service from our excellent crew, and again we hasten to assure any of you who may feel slightly apprehensive about this flight that nothing, I repeat, absolutely nothing can go wrong...go wrong...go wrong...go wrong...go wrong..."