Delta Air Lines was the first to try to convince travelers who are considering using the train or bus to travel between New York and Boston or Washington to fly instead. Delta began by offering cheaper fares on Shuttle flights and now Delta SkyMiles and Northwest WorldPerks members can earn 2,500 bonus miles on each Delta Shuttle one-way flight flown through July 26, 2009 between New York (LaGuardia) and Boston or Washington, D.C. Reagan National. The bonus is in addition to the standard 500 miles earned for each Shuttle flight, which means members can earn a total of 6,000 miles per roundtrip flight with the bonus. Complete four roundtrip Shuttle flights and you’ll be just 1,000 miles away from a roundtrip domestic award ticket at 25,000 miles. Registration is required at http://www.delta.com/shuttlebonus or nwa.com/offers/deltashuttle and there is no limit to the number of miles you can earn. The bonus offer only applies to Delta and Delta Connection nonstop Shuttle flights in the following fare classes, which includes discount fares: F, A, J, C, D, S, I, Y, B, M, H, Q, K, L, U, T.

American Airlines is matching Delta’s offer of 2,500 bonus miles on flights between Boston and New York. Through July 26, 2009, American Airlines is offering 2,500 bonus miles one way on American Eagle’s nonstop service between New York (LaGuardia) and Boston. Fly roundtrip between the two cities and you’ll earn 5,000 bonus miles. There is no limit to the number of miles you can earn with this promotion. The bonus mile offer applies to new reservations on American Eagle nonstop flights only and registration prior to travel is required. Visit http://insideflyerus.wpengine.com/link/?1642

And US Airways has entered the shuttle battle with their offer of 2,500 bonus miles (on top of the 500 you normally earn) every time you fly between D.C., New York or Boston. You must register before you book your travel and complete travel by Aug. 15, 2009. The promotion is valid for US Airways Shuttle operated flights only. Visit http://www.usairways.com/summershuttle