1.   The shuttle offers hourly flights linking New York and Washington.

2.   And US Airways began a new service, hourly flights between La Guardia and Dulles International Airport outside Washington.

3.   United, which has a hub at Dulles, responded to the challenge from US Airways by adding its own hourly flights to La Guardia and Logan from Dulles.

4.   The switch for US Airways is particularly important because the airline makes hourly flights back and forth between the airports.