A lecture about English
A linguistics professor was lecturing to his English class one day. "In English," he said, "A double negative forms a positive. In some languages, though, such as Russian, a double negative is still a negative. However, there is no language wherein a double positive can form a negative."

A voice from the back of the room piped up, "Yeah, right."

Blind pilots
One day at a busy airport, the passengers on a commercial airliner are seated, waiting for the cockpit crew to show up so they can get under way.

The pilot and copilot finally appear in the rear of the plane, and begin walking up to the cockpit through the center aisle.

Both appear to be blind. The pilot is using a white cane, bumping into passengers right and left as he stumbles down the aisle, and the copilot is using a guide dog. Both have their eyes covered with huge sunglasses.

At first the passengers do not react; thinking that it must be some sort of practical joke. However, after a few minutes the engines start revving and the airplane starts moving down the runway.

The passengers look at each other with some uneasiness, whispering among themselves and looking desperately to the stewardesses for reassurance.

Then the airplane starts accelerating rapidly and people begin panicking. Some passengers are praying, and as the plane gets closer and closer to the end of the runway, the voices are becoming more and more hysterical.

Finally, when the airplane has less than 20 feet of runway left, there is a sudden change in the pitch of the shouts as everyone screams at once, and at the very last moment the airplane lifts off and is airborne.

Up in the cockpit, the copilot breathes a sigh of relief and turns to the pilot: "You know, one of these days the passengers aren't going to scream, and we're gonna get killed!