This is not true. There are flights beginning with TN operated by both foreign and domestic carriers, there are flights beginning with TN that are an N-number if you remove the T, and there are flights where if you were to remove the T, it’s not a valid N number – those are of unknown origin.
Prefixes can be 1, 2, 3, or 4 digits. I’m not sure about “officially,” but working at a flight tracking company, I spend a fair bit of my life in the reality of flight plans.
I would say approximately 30% of bizjets operate with the Tango prefix on their reg
Quite a guess, but the actual percentage of non-airline flights operated with an identifier that begins with TN is 3.89%.
It’s a shortcoming in the ATC system that L is prepended to lifeguard flights. Even if you think it’s wrong, we’re actually compensating for this and it certainly reduces confusion without creating any. Even operators of lifeguard and air taxi flights regularly don’t know about the prefix that gets prepended; ask our support staff. If you want to talk about inconsistencies, you’ll notice that L is never prepended to airline flights even when they’re operating as a lifeguard.