is it even in the top 5 biggest dangers?
Statistically I think they’re about at the bottom of the list. But they’re certainly the most, I dunno what the word is. Most accidents are pilot error. Many, if not most of those errors happen before the plane takes off. Many before the engine is even started. But with a midair, now matter how diligent you are in making sure you, the plane and the weather are suitable for flight, another plane gets you.
Fortunately mid airs are not as frequent as they could be. BUT, think about it, we have a whole system, a morass of rules, fundamental training that stresses how dangerous it can be, colliding with another plane, at least my training was like that. We have ATC, whose main job is to prevent airplanes from colliding, we have procedures, specialized airspace, altitude rules and recommendations all designed to prevent midair collisions.
I have about 800 hours now of flying, all as a private pilot. I have had 5 instances off the top of my head where if I didn't react I would have had a mid - air. One was a very close call near a VOR with a plane I'm convinced did not see me. One during my initial training with my instructor, he was yelling at me over a radio call I screwed up. It was quite a little tantrum, I only had about 7 hours, I'll have to admit, I am very capable of getting this type of reaction out of people, but this was underserved. And it was uncharacteristic of him. Anyway, we were inside a busy delta and he wasn't looking outside. So I focused outside while he droned on. I saw a little spot that wasn't moving. I focused on it, and it was growing. So while he was droning I yelled "traffic, traffic, traffic", he stopped, surprised, looked up and said " where?", I pointed it out, he took the controls, turned us, a Mooney, going faster than I had ever seen a small airplane go zipped by very close to us. He never moved and never saw us. My instructor said, "That was close, I guess you made up for that radio call." I told him, "don't you ever talk to me like that again."
Needless to say, that incident gave me huge respect for other airplanes and avoiding them. I fly in a pretty busy area, I get flight following for most flights. I get turned about every other flight for traffic avoidance.
I've run into a few pilots over the years who never worry about traffic. That's scary IMO.
Fortunately most pilots are on the ball and mid-airs are relatively rare. But the potential is always there. Never let down your guard.