The once every >X years traveller. I've seen plenty of them. They are completely overwhelmed with the whole process, appear at the check-in with their stuff in plastic bags, totally unprepared, are totally bewildered by everything, have no idea what to do in the security line and start queuing for boarding 15 minutes before the boarding is supposed to start and/or get somewhat angry when everybody (i.e. FF and premium classes) get to "cut" the waiting line.
It's somewhat frustrating to see these passengers, especially given that all airlines publish extensive information regarding air travel. And I can't think of any transportation system, where the transporting company guides the passenger as extensively thru the whole process.