Sky-writing airplanes: the planes that have lines of smoke behind them. What are they? What do they emit?

Question

I've seen a large number of them in the air over Sardinia and the locals are all questioning what they are about. They aren't writing anything, just making straight lines in the air.

Do you know why they do this? Do you know what they emit?

There are various conspiracy theories as to what these planes are doing. One idea is that they are to create rain. Any substantiated ideas?

Answer 1

There are some kind of trials:
The first kind: Sometimes at high altitudes there are condition in which water is still steam although at that temperature and pressure should become liquid, this because water needs something to condense around and when the wings pass trough this region water condense around the wing , so the trail is like a cloud, made of little water drops.
The second kind: in all combustion engines the chemical reaction of combustion of hydrocarbons:
CH3-(CH2)n-CH3 + O2 => H20 + CO2
This reaction produces CO2 and a lot of water steam, and when the temperature is low this steam condense, so you can see large white trails.

Answer 2

As far as the aircraft that leave the lines in the air, those are not sky-writing aircraft. What you are seeing is contrails left by the aircraft. When a aircraft reaches the higher altitudes the exhaust, which is at a very high heat, mixes with the cold air and creates a cloud like substance - also known as contrails. They are usually just commercial aircraft of military aircraft.

Answer 3

a lot of the aircraft are bi-planes the wings are kind of stacked separated about 10feet bottom to top stabbers in flight also b-52s they fly forever straight across the whole sky one big white line going Threw my mind

Answer 4

sky riding airplanes are airplane to write messages to loved ones like 4 instance I LOVE YOU!

Answer 5

its water sprayed into the exhaust or steam--