How massive airplanes takeoff and stay in mid-air

The Wright brothers successfully flew their first "flying machine" in 1903. Since then, technology has come a long way. This video explains how huge airplanes that weigh over 1 million pounds are able to fly in mid-air without falling. Following is a transcript of the video.

Source: Jim Gregory, Professor of Mechanical & Aerospace Engineering at Ohio State University

Footage courtesy: Stefano Ciciarello

How do massive airplanes fly?

Some of the largest commercial airliners can weigh over 1 million pounds. Compare that to today's heaviest flying bird - the great bustard - which weighs just around 35 pounds. Despite their differences, these two behemoths rely on the same principles of flight.

Flight is basically a battle against Earth's gravity, and your greatest ally is the air. Birds and planes, alike, fight gravity by manipulating the air molecules around them. When birds flap their wings, they're generating an area of high air pressure under the wing and low air pressure above it.

The same happens when planes race down the runway. The pressure difference above and below the wing creates a net upward force, giving the aircraft lift. Once this upward force exceeds gravity's downward pull, you have liftoff! Of course, a 1 million-pound plane needs greater lift to get off the ground than a great bustard.

Planes achieve this with a combination of two things:

1) Airplanes race down the runway at 150 - 180 mph, creating fast moving air across the wings.

2) and something called the "angle of attack."

You probably noticed that planes tilt up at liftoff, instead of rising parallel to the ground. The reason is that the tilt, also known as the angle of attack, directs more air below the wing. This increases the pressure and gives the plane an extra boost.

Once aloft, the main thing keeping the plane in mid-air isn't magic - it's the engines. Engines propel the plane forward, keeping a steady flow of fast-moving air across the wings. This creates that key difference in air pressure that supports the plane's weight against gravity.

But as you fly higher, the air becomes thinner, so the plane must travel faster to maintain lift. While liftoff speed is around 170 mph at sea level, a commercial airliner's cruising speed is around 550 mph at 40,000 feet - where the air density is 10x thinner.

But a thinner atmosphere means less drag on the aircraft, so the engines can hit high speeds with less fuel. Cruising altitudes between 35,000-40,000 feet are the sweet spot where pilots can fly as fast as possible while burning the least amount of fuel.

Each day, more than 2.5 million people in the US hop on a plane, taking to the sky the same way birds have been doing for millennia. Consider that, the next time you're given a safety lesson on how to fasten your seatbelt!

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