A US Airways flight was delayed three hours Monday after a de-icing vehicle clipped the side of the plane, airline officials said. The plane was set to leave Logan International Airport Monday afternoon when the vehicle hit the side of the plane just before takeoff. The aircraft was taken out of service. No injuries were reported, said Liz Landau, a spokeswoman for US Airways. “We obviously apologize for the inconvenience, but safety comes first,” said Landau. Passengers were transferred to another plane, and the flight to Philadelphia took off three hours late.