What is coming out of airplanes that leaves trails sometimes and not at other times?

Question

I have observed that at times planes fly and the white stuff disappears right away; others times it lingers for a very long time and fills the sky. Sometimes planes leave a checkered pattern. What is this????

Answer 1

What you are seeing is not smoke but condensed water vapor. When the air is sucked into the engines it is compressed and when that compressed air comes out the water vapor in the air is rapidly cooled and condenses. On days that are dry that is why you do not see any trails behind aircraft. Depending on the level of humidity in the upper atmosphere will depend on how long you can see that water vapor before it dissipates back into the air.

You can also see it when large airplanes take off. Look at the wing tip and you will see a swirl of condensed air rolling off on the wing tips.

Answer 2

if you read some article about "chemtrails," then just forget you ever read it. Contrails form on the tips of aircraft's wings at certain times depending on that aircraft's height and conditions in the atmosphere. The atmospheric conditions will also determine if that trail quickly disappears or lingers for a long time. A lot of people say they have seen long-lasting contrails (or chemtrails, whatever) cause the entire sky to turn overcast. Usually that's because a front is moving in and the people just didn't know it. As the front moves in, the amount of humidity the air can hold begins to drop, and the sky begins to turn overcast (or large clouds develop). Any airplanes that happen to fly by while the front is moving in will leave long contrails because the maximum level of humidity in the air has already been reached and it can't reabsorb the water that condensed in the aircraft's wake.

The checkered patterns often occur when you live near an airport and you have plains coming and going different directions. A lot of people who see this phenomenon actually live near small airports and don't know it.

Answer 3

One of the combustion products of petrol and other aircraft fuel is water.This water comes from the exhaust and tries to raise the relative humidity of the air behind the engines.At the same time,the heat generated by the engine tends to lower the relative humidity by raising the temperature.Under certain conditions,the net result is to raise the humidity to the saturation point so that a cloud is formed behind the aircraft.But this is possible only when the air temperature is below a critcal value.This value varies with height.At a height of 50000 feet,this critcal temperature is approximately -45(minus forty five) degrees celcius.If this critical temperature is not available at that level, then condensation trails are not formed.
Once a trail is formed,it broadens by diffusion in the air growing bigger sometimes.Because of the extremely low relative humidty ,normally found in the region, exhaust trails are usually not visible.However if the temperature is very low,then even a small increase in moisture content will saturate the air and persistant condensation trails may be formed.This trail will be lingering on till the ice particles in the trail fall out as snow,in the atmosphere.

Answer 4

Well, Petey is close! It's one of two interactions one is between the warm, moist air from the exhaust and the cold dry air of the atmosphere. The warm, moist air can freeze after it exits the engines' exhaust. These are called contrails.

Another mechanism involves the wings during major manipulations of the airplane's controls. As the air travels over the wings and speeds up, it cools. As it cools, it condenses, and you see the water vapor. This reaction is VERY quick and doesn't last very long as the air returns to its former temperature. If you ever watch a video from a camera onboard a fighter jet doing aerobics you can see this reaction, usually. It's fun to watch.

Perhaps it all depends on altitude. Contrails generated at higher altitudes take longer to dissolve due to the smaller temperature differences and the fact that what's happening at these higher altitudes FREEZES. Don't get your panties tied into too much of a knot over this, Asker.

Answer 5

ITS CALLED A CONTRAIL AND IS A REACTION OF COLD MOIST AIR INTERACTING WITH HOT JET EXHAUST.