I think 'Chivalry' is...and always has been..a bit of a myth.
Where does the term come from?...yup, the Medieval Knights.... though, there was nothing very chivalrous about them.
A bunch of Rich Playboys, whose idea of Warfare, was to charge, fully armoured..and atop an armoured Horse, into a wad of lightly armed peasant conscripts, armed with little more than Farming tools, hacking and slashing as they went!....even if unhorsed, they had a very good chance of survival, as the enemy would want them alive for ransom.
As for WW1 flyers?...well, there must have been a bit of "well, if I'm nice to them, when they've survived perhaps they'll be nice to me if the shoe is on the other foot?"
They all were of coarse 'Human Beings' also....and contrary to popular belief...unlike animals..we DO have empathy for each other (we're social animals after all)...but it has little to do with Chivalry (imho)