** FILE ** Passengers deplane from a US Airways jet at Philadelphia International Airport after the aircraft returned to the field on Thursday, Sept. 6, 2012, following a tip to authorities that an explosive liquid was on board. (AP Photo/Matt Rourke)

Photo by: Matt Rourke

** FILE ** Passengers deplane from a US Airways jet at Philadelphia International Airport after the aircraft returned to the field on Thursday, Sept. 6, 2012, following a tip to authorities that an explosive liquid was on board. (AP Photo/Matt Rourke)