Why do some planes leave a trail of smoke behind? Shouldn't this happen to all?

Question

We often find a trail of some when we look up in the sky. But this only happen to some. Is there a scientific reason? I am sure this does not happen to all the planes that are flying high.

Answer 1

It really depends on where the plane is flying and how its flying, different altitudes create different affects after the plane, also the type of propulsion has an affect on whether the plane leaves trails or not, jet planes often do, while prop planes don't as often. The trails are actually just condensation vapor being left behind the plane by its engines' exhaust.

Answer 2

All planes would leave a "smoke" trail if they all flew in the same atmospheric condition. The "smoke" trail, also called a contrail, happens when the plane is flying at an altitude where the moisture content and temperature of the air is just right. The contrail is actually tiny ice crystals formed from water in the exhaust of the airplane.

Answer 3

Many Jet and piston engine planes produce smoke when first starting up on the ground, or when rapidly accelerating to lift off speed. Once airborn, few airplane engines produce smoke unless they suddenly cut in an after burner and accelerate to high speed.

What you see in the sky as passenger planes, transport planes, and military aircraft pass ovehead is a contrail.
that is a line of disturbed air and moisture which was violently spun by the passage of the aircraft through moist air. Contrails usually are produced at the tips of wings and are the byproduct of wind vortices which are separation points between calm air and violently whirling air.

Contrails are not smoke. They are disturbed moist air.

Look at clouds...moist air as opposed to dry air.

So contrails might be compared to wing tips making little clouds in a long line...

Answer 4

While the above answerers have it right, that the trails left by airplanes are caused by condensation of water vapor / ice crystals, I think it is important to note that in a lot of cases it is possible to see actual smoke as well, particularly when aircraft are at full power. If you observe any large jet aircraft taking off, you can see a trail of faint dark brown gas behind each engine.

Answer 5

It is not smoke it is vapor

Contrails or vapor trails are condensation trails and artificial cirrus clouds made by the exhaust of aircraft engines or wingtip vortices which precipitate a stream of tiny ice crystals in moist, frigid upper air. Being composed of water, the visible white streams are not, in and of themselves, air pollution. However, contrails generated by engine exhaust are inevitably linked with typical fuel combustion pollutants.