Why do airplanes..............?

Question

leave a trail a cloud behind them when they are at high altitude?

Answer 1

Contrails are clouds made from water vapor that condenses then freezes behind a plane engine. Since the engines are on constantly, it seems a bit odd when you see contrails with gaps in them, or even contrails that stop and start. If the engine is pumping out a constant amount of water, then why is the trail not constant? This puzzle is sometimes seized on by people who think that persistent contrails are actually “chemtrails”, or some kind of deliberate spraying operation.

But it’s actually very simply. The amount of water in the exhaust is pretty constant, but the amount of moisture in the air is not. The humidity varies with altitude, and a layer of low humidity can be sandwiched between two layers of high humidity. As a plane climbs or descends through this layer, then the trail will only form in the areas of high humidity, and so look like it was “switched off” in the area of low humidity.

You can get the same effect with temperature. A warm layer of air can actually lay on top of a colder layer in what is called an “inversion” (you’ll hear this on the weather sometimes, referred to as an “inversion layer”). When a plane flies through this inversion layer, the trail can be “broken”.

It’s not just climbing or descending flights either. The boundaries between these layers is not flat, and gravity waves or rising convection currents of air can create large volume of air that differ in temperature and/or humidity from the neighboring air, and so can break (or make) the contrail when then plane flies through them.

Don’t take my word for it though. Do a Google search for “broken contrail” and you’ll find lots of examples, and similar explanations (Click the photos above for two).

Answer 2

The trail is unburnt fuel that turns to ice droplets since it is so cold high up, since there is so much water in fuel. then when it melts it falls to the earth or joins the clouds and falls with the rain

Answer 3

It is not "unburned fuel."  (That's a ridiculous answer.)

And it certainly is not "chemtrails" of sinister poisonous gasses.  (That is worse than ridiculous--it's criminally ignorant.)

The air is very cold at high altitudes, and the exhaust of a jet engine is very hot, and contains much water vapor.  When the hot exhaust comes into contact with the cold air, the water vapor condenses into droplets and then freezes into ice pellets.  These make a visible trail called a contrail, for "condensation trail."

Jet airplanes are the ones that are most associated with contrails, but turbo-prop and piston engines do it also.

Answer 4

Not all do.  The B-52 leaves a cloud of black smoke when they take off.

Answer 5

I've been spreading chemtrails for the past 26 years. (I'll bet that John B and Aviophage have spread their share of 'em too!) The chemicals are carbon dioxide and water. Nothing more.

The chemtrail hoax is a bunch of bogus rubbish.

Answer 6

its chemtrails

For over a year, the military has been spraying the skies throughout America, Canada, and now parts of Europe (including Britain, France, and the Netherlands) with substances that were initially referred to as "mystery contrails" , but later were named "chemtrails" by investigative reporter and author William Thomas.  When questioned, military and government officials either deny any knowledge of these sprayings outright or they offer unbelievable  and ludicrous explanations that only a moron could believe. Joe Burton has been aggressively investigating and reporting on this story from early on. Apparently he had been too aggressive, because his house had been targeted for direct spraying by low flying, unmarked aircraft.  In a story posted  Feb. 15, 1999, Joe reports the physical symptoms that his family and his pet have been experiencing from the sprayings. Joe believes that many of these military tankers responsible for the sprayings are remote controlled aircraft, but Al Cuppet (6 years with the US Joint Chiefs of Staff) has told radio talk show host  Jeff Rense during interviews on June 1, 1999, May 16, 1999, and May 7, 1999 felt that many of these tanker planes were more likely being flown by foreign pilots, possibly Chinese or Russian

Answer 7

What you are referring to is a vapor trail which is formed when the hot vapor from the engines is exposed to the cold air in the high atmosphere.  You form your own vapor trail when you breathe out on a cold day, and you can see your breath.

Answer 8

Chemtrails...seriously???  

You people are really, really messed up in the head if you believe anything remotely like that.

Answer 9

That's their exhaust. (very hight temperature).

Answer 10

It is formed at all altitudes, not only in high ones. It is their exhaust. And its not hot. Its like the exhaust of cars and such. But cars nowadays have filters to stop emitting these. Basically its just the soot of the burnt petrol.