Two armed F-16s from Andrews Air Force Base were scrambled — sent into the air quickly — and escorted Flight 1814 to BWI, its intended destination, said Maj. Ed Thomas of the North American Aerospace Defense Command, or NORAD.
The Airbus 319, with 45 passengers and a crew of five, had taken off from Charlotte, N.C., shortly after 8 a.m.
Laura Brown, a Transportation Department spokeswoman, declined to say exactly what happened, describing the incident only as "a miscommunication between the pilot and the ground."
FBI spokesman Barry Maddox initially had said a code indicating a problem on board was incorrectly entered into the plane's radar transponder, but later confirmed that he had erred.
Passengers were released from the plane shortly after 11 a.m., or about 1½ hours after it landed at BWI.
Those interviewed afterward said they did not see the fighter jets and were unaware anything was wrong until after the landing. The first indications, they said, was that the plane seemed to taxi for longer than normal and police cars came into view.
"Seeing all the cops flipped me out," passenger Jill Lantz said.
Arthur Ramsey of Greenville, S.C., who was flying to Baltimore on a business trip, said about 30 minutes after the plane landed, the pilot told passengers there had been a miscommunication and the crew was trying to take care of it.
"The pilot was really nervous. He didn't have a clue — you could hear it in his voice," Ramsey said.
Two FBI agents boarded the plane and went directly to the cockpit, Ramsey said. Other agents and police officers appeared to be searching the baggage compartment.
"At first we were all kind of joking about it," Ramsey said. "But the more cop cars that showed up, we knew it was serious. A lot goes through your head in a situation like this because they weren't giving us a lot of information."