Because he would just be a terrorist, like those guys at Gitmo.
The Germans sometimes talked of treating Allied "terror bombers" as terrorists, but I don't believe they ever did, officially, at least. Captured airmen were certainly kept as normal POWs in POW camps.
Same goes even for RAF personnel who had been flying in support of the resistance in occupied countries.
"US weighed POW protections in releasing Saddam images: defence official" -