Craig Smith, age 7, of Lititz, Pa., for his question:

HOW DOES A HEAVY AIRPLANE FLY?

An airplane is a heavier than air flying machine. A large transport plane can weigh over 350 tons, yet it can zoom down the airport's runway and take off into the air.

Giant airplanes, and all planes for that fact, fly mainly because they have engines to give them power and carefully designed wings to give them lift    or upward movement.

An airplane's engine or engines move the craft forward. As the plane moves, the air that flows over the wings has less pressure or weight than does the air under the wings. This difference in air pressure lifts the plane and keeps it in the air.

During the 1800s inventors made the first gasoline engines which could give a plane the power it needed for flight, and on Dec. 77, 1903, two American bicycle manufacturers, Orville and Wilbur Wright, made the first powered flight.