us airways upgrade to first class at airport

Virgin America offers last minute upgrades (4 hours before flight time) to its luxe first class cabin for between $70 and $270 each way depending on the length of the flight, and US Airways has a similar program called "GoUpgrades" allowing passengers to upgrade from economy class to first class for $50 to $500 each way, depending on flight length, 24 hours or fewer before flight time.
us airways have comfortable First Class cabins on most flights within the United States, Mexico, Latin America and the Caribbean.

http://www.usairways.com/EN-US/TRAVELTOOLS/INTHEAIR/ENVOYFIRST/GOUPGRADES.HTML

GoFirst is available beginning 24 hours prior to departure on domestic flights for $50-$500, depending on length of flight.

Upgrade your flight when you check in online, at the airport or call 800-428-4322/TTY 800-245-2966 or 800-622-1015 (international). Upgrades are sold based on availability.

If you're Preferred, you can still enjoy complimentary upgrades when you travel in North America.

Terms & Conditions
Upgrades are available for purchase on flights for which a customer holds a confirmed, paid ticket. Upgrades are not available for stand-by passengers. Payment of upgrade is due before a seat assignment will be made. GoUpgrades can be purchased up to 24 hours prior to departure. GoFirst North America upgrades are available through Reservations and at the airport.