6m - G0OQK and aircraft

G0OQK (98km) is coming in here regularly today on 6m WSPR. Looking at his traces on my WSPR screen, there is clear evidence of airplane involvement:  most 2 minute transmissions appear with 2 or 3 Doppler shifted lines, suggesting planes along/crossing the path between us.

What I cannot be 100% certain of is if the path would "work" without airplanes As all successful decodes seem to be when there is evidence of planes, I think the path is only possible when there are planes, but honestly I am still unsure.

The last decode at 1124z had drift (probably Doppler) of 3Hz, which is a lot. Sometimes the drift/Doppler was 0Hz. So far this morning Nick G0OQK has been seen 9 times. The other Nick G4IKZ (18km) has seen me countless times, but he is very local.

Interestingly, G4IKZ had 0Hz Doppler/drift on all his spots overnight of G0OQK. The distance is 83km with crossed polarisation (I think).  Perhaps this is evidence of pure tropo? At night few/no planes etc..