I guess the timing was fortuitous. For explanation see below.
You can’t live in this world with your eyes open and not see the vapour trail of a jetliner crossing the sky.
But I’ve never seen the line drawn in the sky in front of the ‘plane. Maybe it was a learner pilot who needed a road to follow.
Na! It was the sun casting a shadow onto the atmosphere that obviously had enough moisture in it to catch the shadow. I tried to take a shot of the sun behind the ‘plane but it was too bright and my camera had a hissy-fit and wouldn’t respond to instructions. So, sun at opportune angle of elevation. Sun in opportune direction. Aeroplane going in same – coincidental – direction. Moisture level of atmosphere. Camera at fortunate location. Daughter in passenger seat on the bestest possible place to see it and say, “Dad! Stop. Look at that!”
Pretty lucky doncha think!