Southwest will fly into TTN when pigs fly. The Mercer County NIMBYs who live near the airport have put up an intense fight to the proposed modest terminal expansion. If SW ever proposed service to TTN, the NIMBYs would throw a major fit.

If I remember right there are also issues with the runways - they would have to be upgraded to allow major commerical operations.

Anyway, I live only a few miles from TTN, and would love to see SW there!

US Airways Express (Shuttle America) has two daily flights from TTN to PIT. That's it as far as scheduled commercial operations go.