even if the flights are full, I don't see them as a risk.
one - everyone is wearing a mask.
two - according to latest what I've read, contagion happens mainly if someone infected expels big droplets. for this to happen, they need to breathe heavily or shout etc (and not be protected).
on a plane, even though you're sitting next to each others, under normal circumstances you aren't shouting at each other etc and you're simply breathing normally / calmly.
remember a few weeks back some dickhead took a plane from madrid to tenerife? the guy that couldn't wait for his test results and when he landed he found out he was positive? well, no one got infected on that plane.
I'm not saying it can't happen, but having dinner in a restaurant inside somewhere with friends (where no one wears a mask) IMO is more 'dangerous' than boarding a plane with everyone wearing a mask.
just my opnion really.