Planes stay in the air thanks to combination of lift and thrust

Who hasn't looked at an 800,000-pound passenger jet soaring through the sky and wondered how it could possibly stay up there?

Ten-year-old Lucas took a break from munching his nachos at Schaumburg's Pilot Pete's restaurant long enough to ask, "Why don't plane's fall down?"

Lift, thrust, weight and drag are to thank for the phenomenon of flight. When you're cruising through the clouds, you've got those powerful forces keeping you and your fellow passengers airborne. Of course, there's more to it than that, so here's the scoop on flight.

First, the massive weight of the jet must be overcome so it can fly. That's why it needs thrust. The engines suck in air with a fan at the front of the jet. That air is compressed, sprayed with fuel, and ignites to become burning gas. Powerful streams of gas shoot backward, thrusting the jet forward.

Now that the power is on, the jet needs lift so it can gain altitude. The shape of the wings forces the air on top of them to move faster than the denser air below, thus, providing lift.

But there's still all that weight to consider, along with drag - the force that's trying to fight the jet's forward motion. (You can feel drag when you're walking against a strong wind.)

Aircraft are built so their weight is spread from front to back and designed to let air pass around them. The wings' lift additionally balances the plane's weight, and the thrust is stronger than the drag. So even with all that resistance, thrust and lift win.

The science behind jets may be remarkable, but there's one more key aspect of a safe flight - the pilot. He or she is responsible for the safety of the plane and passengers. This begins before takeoff as the pilot checks weather conditions and goes through a series of safety checklists, and continues until everyone's departure from the aircraft.

When all the scientific forces are working together under the guidance of a highly trained pilot, people can hit the skies to take vacations, visit loved ones, attend business meetings and explore our amazing world.

• Sources: nasa.gov, science.howstuffworks.com, and "Why Do Airplanes Fly" by Rob Moore.

Did you know?

• Approximately 100,000 planes take to the sky each day in the United States.

• A Boeing 747-400 weighs more than 403,000 pounds empty, 875,000 pounds full of passengers and fuel, and can reach a top speed of 628 miles per hour.

• Newly hired commercial airline pilots already have about 4,000 hours of flight time.

• In 1952, the United Kingdom's de Havilland Comet became the first jet aircraft to go into regular passenger service.