[RiK]

If you look at a website called flightradar24 you can track flights in real time . It gives the airline name height speed , the destination and  take off point . As the plane passes overhead you can confirm with binoculars the identity of the plane via the livery &  colours . They were leaving long lasting and spreading vapour trails this morning all along the designated air ways . I found that these were flying between 30,000 and 36,000ft , looking at the temperature at that height which was about 60 below zero , plus the humidity and the dew point numbers would explain this .There's another site  where you can get this info' from , between ground level up to about 45000ft. Planes leaving shorter contrails were flying nearer 40,000ft which had much drier air and corresponding  dew point . They were all commercial airlines not military or unmarked .

Air traffic has surely increased over the decades it's busier than ever up there and no doubt artificial cloud layers formed by vapour trails could affect the amount of sunlight to a degree as a result , I'm sure there are more sophisticated ways of geoengineering . Who is it that loads the chemicals at Glasgow airport on on an Easy Jet flight bound for London Heathrow and where is all the equipment stored ?