MrMan wrote:The_Adventurer, how old are you? I remember seeing trails like that behind airplanes all my life. Have they stopped doing that in recent years? Come to think of it, I haven't seen those in the US for a long time. Did the EPA get onto the airlines and make them hold back on the emissions?
Vast ignorance as usual from the conspiracy wingnuts.
Water vapor has always been a byproduct of jet propulsion. In fact, there is something called a "wet takeoff"
Where water is mixed with fuel to increase takeoff thrust.
Contrails are water vapor and other exhuast. I don't know how much the EPA has been after the industry, but big changes have taken place with engine design based on the push for fuel economy and noise reduction, which obviously can affect the amount of water vapor output.
Other factors are altitude, atmospheric conditions and the type of engine the jet is using.
Vapor trails have existed since the advent of the jet age.
When we are in Oregon we live in a flight corridor, and vapor trails are visible most clear days.