Why do airplanes suddenly lose altitude?

Question

Why do they sometimes drop into thin air causing your stomach to feel queasy?

Answer 1

The actual science behind it is pretty complicated, but it's due something called turbulence. Air is not consistently dense, nor is it standing still - there are updraughts and downdraughts and winds that blow in many different directions.

There are three types of turbulence, strong winds close to the ground (this is pretty easy to understand, the wind blows the plane about), storm clouds and clear air turbulence.

Storm cloud turbulence is caused by downdraughts (caused by cold air, which sinks) and updraughts (caused by hot air, which rises) - kind of like a wind that is blowing upwards or downwards. If a plane suddenly flies into a downdraught the "wind" will blow it downwards. Because planes travel so fast this doesn't usually happen for more than a few seconds.

Clear air turbulence is caused by the jet stream - very fast moving winds that travel high in the atmosphere from west to east. In the middle of the jet stream the winds are pretty constant, but on the outside the rest of the air is shaken up, causing turbulence.

Turbulence is uncomfortable, but it's not dangerous. Pilots have known about it almost since flight began, and all aircraft and pilots have methods to reduce the effects of it. Even in the most extreme circumstances turbulence is rarely more than a few bumps.

Answer 2

When you open a bottle of Coke, or whatever carbonated drink it may be, you notice bubbles rising to the surface of the drink. When the surface of the planet heats enough in a particular spot or area, bubbles of hot air form and rise into the sky in the same manner as the drink bubbles. Now imagine one of those bubbles is, say, 200 feet in diameter. The air inside that bubble is less dense than the surrounding air, due to it being warmer. An airplane comes sailing along, happily flying in air that is a certain density. Suddenly it flies through the bubble and the wings don't have quite as much support as they did a moment before. The wing falls through that warmer, less dense air because the plane is set up for cruise in the more dense air. It takes it a second to catch up with the new density, and by that time it's already through the bubble and back into the more dense air. You feel that as a bump, or drop. There is absolutely no danger, and pilots feel these bumps virtually every time they fly, at some point in the flight. That type of turbulence usually ends at the top of the cloud deck, and once the plane is above the clouds, the air is normally smooth again.

Answer 3

Turbulence
Air behaves according to the same laws of motion as water. Picture a river flowing along, with its various conflicting currents, rocks along the bottom, all interfering with the smooth motion. You have ripples, eddies, portions moving at differing speeds. Air is the same, and the currents conflict the same, it's just that you can't see them. The jet stream you see on the weather segment of the evening news is a major contributor to turbulence across any region, as its effects extend for hundreds of miles. Mountain ranges do the same. and because it's all invisible, there is no way for the pilot of an airliner to avoid these pockets of upset air.
Aircraft designers know this, and safety margins are built into aircraft so that dropping 'into thin air' doesn't break the plane. Pilots will inform Air Traffic Control of turbulence rated as severe so that other planes can avoid the area.

Answer 4

Sometimes they approach pockets of warmer (thinner air) and that causes them to drop in altitude

Answer 5

atmosphereic comditions, the air gets thinner or hot the plane looses lift and falls, ( nothing for the wings to grab on to basicly.) if the air is cold and thick it will climb as long as it dose not climb above what the auto pilot is set at.

Answer 6

because the air 'falls' out from under them - like a pothole on a street
and a bit of low pressure/ turbulence will do that

nothing to worry about - unless you have hot coffee