Just to throw a spanner in the works here, after all the “up to 3 errors are allowed” reassurances.

Some years ago, my wife, before she was my wife, spelled her surname with one “T” whereas the more common spelling of the name was with two “T’s”. She was travelling DL from SNN to ATL, but her ticket was issued spelling her surname with two “T’s”

The hassle she got at the pre check-in security check was fairly serious & it looked for a while like she wasn’t going to be let fly. However after the officer consulted with his supervisor, she was let fly. They also put a note in her booking, to try to avoid similar issues on the return.

But again, at check-in at ATL, the issue reared it’s ugly head again, despite the note in the booking. In the end she did get to fly home, but not without hassle.

So I don’t know, in my one & only experience of a spelling mistake, it sure caused trouble & that was only with one little letter