An aircraft that last flew decades ago is not relevant here.

The comment you replied to says "no commercial aircraft flies at that altitude" and the concorde hasn't flown in decades.

Well.. November 2003, so only after that can you claim "decades", plural.. it's a while yes, but clearly shows that at least it's in the realm of commercial aircraft, and may happen again, in principle.

Edit: By the way, that comment said, and I quote, "Name one plane that flies at more than 60,000 feet, I'll wait."

No word "commercial" there. So, aside from the Concorde, there were/are several others, some already mentioned.

No Concordes any more I'm afraid. There are no military or civilian planes that fly that high -- unless the CIA dusts off a U-2. There is no navigation risk.

In contrast, every orbital launch has to deal with 10s of thousands of pieces of space debris.

Several military airplanes, including fighters, can and do fly that high and more. I never said anything about navigation risks - that was from other posters. Obviously space debris is a much higher daily risk, for satellites.

Um, the Air Force still uses the U-2. As does NASA.

https://en.wikipedia.org/wiki/Lockheed_U-2#Operators

The F-15 and Eurofighter Typhoon have published service ceilings of 65000ft, put them in a vertical climb and they will go a lot higher than that, the Streak Eagle reached 103000ft.

Still can't see any risk. You won't find F-15s flying that high except if they need to shoot a balloon.