You can test out other cities with the following URL:
(replacing XXX with the airport code you wish to try)
Many additional cities have been tried over at Flyertalk without additional success.
Registration can be done separately for each city’s promotion, and each roundtrip originating in that city will earn double elite qualifying miles and bonus miles as follows:
Purchase tickets by November 30 for travel through December 31, and naturally the bonus is valid for travel only on Delta and Delta Connection metal (no codeshares or partner flights). Bonuses can be earned over and over during the promotion period.
It seems like a good time to fly to one of these cities on a one-way ticket and do a bunch of Delta mileage runs (if Delta is your thing, it isn’t mine) originating in that city. Pick a city served by Southwest that isn’t a Delta hub and the fare might be reasonable, pick up 10,000 bonus miles per domestic hop. And 25,000 miles for discount coach international itineraries seems almost unprecedented, like the good ‘ol days of Continental circa 2000 and earning 100,000 miles on a single roundtrip…
This continues Delta’s game of route-specific double elite qualifying miles in specific markets they’re trying to compete, they recently launched triple elite qualifying miles in their shuttle markets (though the triple miles apply only to miles flown, not to 500 mile minimums, so on Washington DC – LaGuardia you’re really only getting a 50% bonus, Go Delta!).
American matched Delta on that one in a fairly market-specific way.
This is a far cry from last year’s offerings of system-wide double elite qualifying miles, the major carriers now seem to be using this as a more targeted tool. Which is of course annoying for those of us not convenient to Nashville, Pittsburgh, Raleigh, or St. Louis.