Carbon credits?
Thanks for the enthusiastic comments, Akira, Paco, Bruno, John, and Fons.
The capture was extremely lucky. I heard the plane but never had it in my sight, likely because I was peeking over the camera with my eclipse glasses so everything else was black, and the camera screen blacks out during exposures. I routinely release the shutter for repeated frames with a 5 sec release delay during solar captures so there was no chance of intentional timing here. But the thought occurred to me that it would have been neat if it had gotten into the frame. When reviewing the frames I was at first wondering what that disturbing blob in my frame was and almost deleted it! Then I was initially a bit sorry I did not quite capture the whole tail, but if I had just been a few millisecond later I would likely have missed the warm exhaust/contrail bending the light of the sun.
The equipment was tripod mounted 300PF protected by Baader Astrosolar ND 5.0 film with stacked TC-14E and TC-20E III on my D500.