On US Airways at DCA I was rudely yelled at several times by the First Class checkin counter agent, "This is the line for first class! First class only! This line is only for first class! The regular line is over there!" She directed these shouts only at me and Mr. GradGirl (both of us are late 20's but by looks might pass for high school age). We just ignored her and handed over the first-class ticket receipts.

I have never experienced age discrimination on Continental first class or business class in Airtran. And internationally, Aer Lingus treated every passenger exceptionally well.