DD20 has flown in and out between MCO & BWI solo quite a few times since about eigth grade. Occassionally, she'll bring a friend along who'll fly back with her and a couple times it was the friend who needed fly home early alone. Flying into MCO is a piece of cake b/c there's no time to kill in the airport, especially if you don't check luggage.
She's had boyfriends who've flown in and out of wdw to meet her when we were there for Nationals during the high school years. They've usually taken ME and have only had carry-on luggage to keep check-in/security simple. Unlike the rest of the family, I actually enjoy the fifteen hour drive but am not especially fond of cooling my heels for hours trapped in an airport so I don't mind transporting everyone's luggage.
I know it's silly, but I feel better about boys flying alone than girls. Either way, if we can mange it, I like to drop off/pick up at one end and make sure the kids are met at the other end. I just feel better seeing them go thru airport security myself and knowing there'll be someone to meet them at the other airport instead of worrying about the endless "what-ifs" that my over-protective-motherly-anxieties imagine could happen during the 2-3 hour wait in the airport before take-off...