For its 40th birthday, Southwest is growing sentimental: The not-so-low-fare carrier is returning to its younger budget roots with fares from $40. (Note: Make that $40 one way, plus taxes; Southwest may be getting older, but it’s not senile.)

The deal, valid on bookings through Thursday (8:59 EST to be exact), offers three tiers of fares: $40 on flights covering up to 450 miles, $80 for 451 to 1,250 miles, and $120 for the greatest distances in its repertoire. For Washingtonians with tight wallets, this means you can go to, well, many places you can drive to, such as Newark or Norfolk, and those you probably have an aunt you should visit or reunion you could attend, such as Albany or Cleveland. Those with more funds to fling around can hit up such party-down towns as New Orleans; Panama City Beach, Fla.; and Nashville, from $80 each way. And in the top tier, the destinations fall along the West Coast, plus a few states with stunning national parks and dry heat (nod to you, Utah and Arizona).

Of course, because it’s Southwest’s fete, it has the princess rights to tell when you have to show up and leave: Aug. 23- Nov. 16, on all days but Friday and Sunday, plus a sprinkling of blackout days.

Southwest, you old dog, happy birthday — and can’t wait for your half-century celebration.