for most purposes out of washington, it's american, united or usairways.

other carriers only enter as a choice if your business flights often take you to Atlanta or Cincinnati (Delta), Newark or Houston (continental), minneapolis and detroit (Northwest) or international destinations.

The quick expiration of Southwest points and the lack of international flights, makes them a poor choice unless you travel a lot in a year and want a domestic flight. Jet Blue has relatively limited service out of Washington and i dont believe it has much on an international connection.