An American Airlines (search) commuter flight was diverted Saturday after a passenger passed a note to the crew demanding to be taken to Australia, the FBI said. The plane landed safely at Washington's Dulles International Airport (search) and the passenger was in FBI custody.

The FBI (search) said there was no indication that the incident involving Flight 4959, operated by American Eagle and carrying 19 passengers and a crew of five, was terrorism-related.

The passenger, whose identity was not released, was being questioned by the FBI. No charges were immediately filed.

"It was nothing other than the unreasonable demands of an unruly passenger," said Debbie Weierman, spokeswoman for the FBI's Washington field office.

The flight left New York's LaGuardia Airport at 10:57 a.m. bound for Ronald Reagan Washington National Airport. It landed at about noon at Dulles, which is 33 miles away.

The FBI detained the passenger after questioning the 23 other people on the flight, said Tara Hamilton, spokeswoman for the Metropolitan Washington Airports Authority.

New York's police commissioner, Ray Kelly (search), said a passenger passed a note to a crew member during the flight claiming that he had a bomb. The passenger later said he had a grenade, Kelly said.

An American Airlines spokeswoman, Lisa Bailey, said that upon approach to National Airport, a threat was made against the plane and the crew decided to divert to the other Washington area airport.