NEW YORK — A commercial passenger jet carrying cargo from Yemen landed in New York under military fighter jet escort and its cargo was searched Friday, as parcels in transit across the globe were scrutinized after authorities overseas found two explosive packages from Yemen bound for Chicago.

No explosives were found aboard Emirates Airlines Flight 201 after a search, FBI spokesman Richard Kolko said. He said the plane flew in to John F. Kennedy Airport under escort as a precaution.

President Barack Obama called the coordinated attacks a "credible terrorist threat." Packages were found aboard cargo planes in Dubai and England and U.S. officials said they were increasingly confident that al-Qaida's Yemen branch was responsible.

The Emirates Airlines plane, a Boeing 777, landed shortly after 3:30 p.m. Passengers walked off the jet on two covered stairways and onto the tarmac, dragging their luggage behind them. Several police cars surrounded the airliner.

The flight crew didn't mention any issue with cargo, passengers said. They were told there was a heightened security concern and that their bags would be searched but weren't told why. They also didn't know about the interest in their aircraft until they saw it on TV screens in the airport and glimpsed the mob of waiting reporters.

"We saw a lot of police and they instructed us that we would be getting on a bus. And that all our luggage would again be screened," said Nick Chan, 32, who was returning to Manhattan from a business trip.

David Packles, a 23-year-old financial analyst returning from a vacation to Thailand, said he hadn't noticed fighter jets tailing the plane and didn't think the 20 extra minutes they spent on the tarmac was that unusual.

"It's a 14-hour flight. Everyone was just kind of exhausted," he said.

Emirates said in a brief statement that it was "cooperating fully with the U.S. authorities" and would provide more information as soon as it was available.

U.S. fighter jets routinely escort airliners when there may be a problem in order to observe the aircraft and be prepared to take any action if necessary.

John Cornelia, a spokesman for U.S. North American Aerospace Defense Command, said the Emirates airliner was escorted by a Canadian fighter based in Bagotville, Quebec, to the U.S. border, where two U.S. fighters from the Barnes Air National Guard Base in Massachusetts took over.

Associated Press writers Lolita C. Baldor in Washington and Tom Hays in New York contributed to this report.