Why does a plane suddenly start producing exhaust vapour trails?

Question

I was watching it flying way up high in a clear sky, apparently at the same speed & altitude but it very suddenly started producing strong vapour condensation trails, and kept on doing this until it went out of view.

Is it a sudden change in air temperature and if so, how come hot air & cold air doesn't just mix in the wind so there aren't such sudden changes in temperature?

Answer 1

i asked this question to our local weatherman, and he said that it is to do with weather conditions, different humidities

Answer 2

The higher the plane climbs the colder it becomes. The engines as you can imagine become very hot and the result is a vapour trail.

Answer 3

Contrails form through the injection of water vapor into the atmosphere by exhaust fumes from a jet engine. If there is sufficient mixing between the cold upper tropospheric air and the hot exhaust gases to produce a state of saturation, ice crystals will develop.

Answer 4

The aircraft was probably still climbing while you watched.  As the plane flew higher it met colder air.  Hot exhaust meets cold air = vapour trails etc.

Answer 5

There is a critical temperature value for a particular pressure ,at which this condensation trails form.If the temperature is above that value they do not form.Even at the same altitude, the temperature value changes from one region(or place) to another.As the aircraft is at a greater height(about 30000 feet usually),it covers a larger area from one side of the horizon to the opposite side(or during the period it is visble to our eye) and there may be variation in the temperature values  leading to the formation of these trials.In some cases the aircraft may have slightly reached a higher level(which we may not be able to find with our naked eye)where temperature conditions are favourable for the formation.

Usually each aircraft is assigned one particular level for flying and that aircraft may be assending to that level immediately after take off which is likely to take a few minutes.

Answer 6

Passengers not allowed to  smoke in plane so they have to go outside for a ciggy hence a trail of smoke