My younger brother was obsessed with planes from a young age. My father would take us to air shows and he could identify virtually any WWII plane by the age of 7 (most from the ground while they were in flight). He got his pilot's license before his driver's license and went on to become an engineer. He got married and has a good job, has friends, is not weird. No one has ever suggested he was on the autism spectrum (and he is not). He still flies (but also likes rowing and running).

In short, I would accept this as one of his quirks and not worry too much about it.