This morning there was quite a dramatic sunrise with some interesting clouds and contrails, and I was taking some photos. I live fairly close to Heathrow and planes often pass over fairly low on approach to the airport.

I saw a plane passing over and thought it might add some interest to a photo silhouetted against the clouds so I got the camera ready – and was then surprised to see it starting to leave a contrail even though, visually, it was clearly at quite low altitude...

This is the first picture, timed at 7:53:18 this morning.

I took a couple earlier through the window and the camera didn't focus properly, but it's possible to see that the trail started between 7:53:06 and 7:53:16. This is the last one in the sequence, at 7:53:38:

Flightradar24 identified it as BAW22E, and there wasn't any other possible traffic nearby that it could have been confused with.

Putting the track into Google Earth at my location also confirms it was the right aircraft.

At the time I took those photos, the plane was at less than 12,000 feet, which seems much too low for a persistent contrail to form.

And yet the trail hung around for at least 15 minutes. Any ideas why this would be?

Weather conditions were frosty after rain yesterday, about 2ºC at ground level. Model sounding shows high humidity most of the way up...