Airtran will let you upgrade to business class from any fare at the airport on a first - come, first - served basis for $ 69 and up per flight segment (that's one take off and one landing), or from higher economy fares in advance; Spirit's
Airbuses have one row of four extra-wide seats at the front of the plane with more legroom for sale at $ 12 to $ 199 if
bought in advance or $ 25 to $ 75 for onboard upgrades, depending on flight length.