Aircraft Trails

[jadyn]

I live on the flightpath of UK transatlantic flights in the UK . Over the last few days, the sky has been particularly clear with very little cloud cover and I've noticed that some aircraft seem to have either very short trails or no trails at all. The ones that have no trails just look like a miniature cigar tube moving slowly but can nevertheless be heard. On the other hand, when light cloud cover is present, the aircraft virtually always have a trail of sorts.
Does anyone know why some of these planes have trails while others do not? Is this down to the weather or possibly the temperature at the height that the aicraft fly?

thanks

[emeritus]

This should explain

http://en.wikipedia.org/wiki/Contrail

[boxtops]

I thought it was to do with the height they were travelling, the temperature of the air they are flying through.

[Teddio]

For every pound of kerosene burned in the jet engine there is a pound of water vapour in the hot exhaust gas. If the temperature is low and the humidity is high, then the water vapour will freeze into tiny ice crystals. This nucleation and growth process is aided by the presence of tiny carbon particles in the exhaust.

[jomifl]

By observing the lengths of vapour trails at different heights you can infer the humidity of the air masses at different heights and from how they change from day to day ,what weather is coming your way

[BertiWooster]

When I were a little lad , and I saw a con trail behind an aircraft - i thought it was something to do with weather forecasting - i.e . the aeroplane flying through the clouds and testing them

[jadyn]

Thanks everyone.

[ChuckFickens]

You can have a bit of conspiracy theory thrown in for good measure if you want.

http://en.wikipedia.o...ail_conspiracy_theory