RAT5,
I don't think there is any mystery in FR's biz model - screw the best deal out of everyone, have eye-popping starter fares, then add on every extra going (a model only improved on by Caribbean startup Flyred!) and make even more from selling add-ons on FR.com website. MOL loves to hate travel agents because he is the biggest travel commission maker in the business! Then complete the picture by profiting from noshows and charging a fortune to change bookings.
So airframes are only part of the picture - a big part nonetheless!