Originally Posted by
vicarious_MR'er
Southwest has determined they aren't willing to deal with the ramifications from FAA if someone lies to them and sneaks an >2 onto a lap. That's their own risk management conclusion, and they are entitled to it.
It's also their own revenue generation conclusion. Southwest serves a lot of families and leisure travelers (higher % than for the other majors), and they've got an interest (quite apart from the FAA regs) that people who are obliged to pay for seats (i.e. >2 years old) do in fact pay for seats.
I really can't imagine that the other US majors would be using a good faith "if the pax tells us the kid is under 2, we'll take their word for it, absent clear absurdity" standard, if they believed that exposed them to any significant regulatory risk from the FAA.