Southwest Airlines is celebrating their 40th Anniversary with $40 Airfares for select markets and select flights 450 miles and under (one way). Flights greater than 450 miles run higher (see below). Travel must be booked by 6/23/2011 and completed between Aug 23, 2011 and Nov 16, 2011. Additional fees may apply, see link for details.

0-450 Miles - $40 one way
451-1250 Miles - $80 one way
1251+ Miles - $120 one way