Reply #9: I like this variant...

[onager]

At a major airport, passengers are preparing to board a fully-booked 747.

The flight crew walks past. The pilot and co-pilot are both wearing dark glasses...and tapping their way along with white canes.

Everybody laughs. What a great joke!

Soon everybody's on board and the plane starts rolling down the runway...

...and rolling...and rolling...and rolling...

...until it's obvious the 747 WON'T clear the tall fence at the end of the runway. It's about to smash thru the fence and go over a cliff, right into the ocean.

The passengers all scream...

...and the 747 suddenly lifts straight off the runway, into the sky, in a perfect take-off.

In the cockpit the co-pilot says to the pilot: "Earl...one of these days they'll scream a little too late, and we're all going to die."