Authorities say a flight from Philadelphia to Boston was delayed and ultimately a different aircraft was used after a couple gained unauthorized access to the plane.

Officials said American Airlines Flight 1655 was slated to depart 8:00 a.m. Sunday, but two hours earlier, a man and woman walked on board through the doorway to the jet bridge and took their seats. The door should have been locked prior to the formal boarding process.

American Airlines officials said the couple was discovered during boarding. They determined the pair was on the correct flight, but the plane was de-boarded, searched and another aircraft was used "out of caution."

WCVB-TV reports the couple didn't speak English.

American Airlines said it didn't consider their boarding a security breach because they had gone through security.