Military jets are escorting a commercial passenger jet to JFK airport in New York.

The flight, which contains a package from Yemen, was escorted by Canadian F-18s to the the U.S. border and has since been picked up by two American F-15s.

An FBI official told Reuters there was no known threat associated with the flight.

Federal authorities were stepping up aviation security precautions after cargo planes were grounded at two U.S. airports in response to suspicious packages that may have been part of a “dry run” for a future Al Qaeda plot.

One of the packages, found on a UPS plane at East Midlands Airport in central England, contained what looked like a toner cartridge with white powder and wires coming out of it. Another package was found at a FedEx facility in Dubai.

Both packages originated in Yemen and may have been sent by Al Qaeda in the Arabian Peninsula, which is based in the country.

The packages, discovered late Thursday night, prompted U.S. authorities on Friday to methodically sweep and clear cargo flights in Newark, N.J., and Philadelphia. Law enforcement agencies are investigating whether the packages were part of a dry-run mail-bomb plot, an attempt to get explosives into the United States or an attempt to send materials to third parties in the U.S. for another plot.

The FBI reported that two of the suspicious packages were addressed to religious institutions in Chicago.

“All churches, synagogues and mosques in the Chicago area should be vigilant for any unsolicited or unexpected packages, especially those originating from overseas locations,” Chicago FBI spokesman Ross Rice said.

Ross would not identify the intended recipients of the packages but said they had been contacted.

White House Press Secretary Robert Gibbs said President Obama was alerted Thursday night, and administration officials have been monitoring the situation.

“Based on close cooperation among U.S. government agencies and with our foreign allies and partners, authorities were able to identify and examine two suspicious packages, one in London and one in Dubai. Both of these packages originated from Yemen,” Gibbs said in a written statement. “As a result of security precautions triggered by this threat, the additional measures were taken regarding the flights at Newark Liberty and Philadelphia International Airports.

Given the origin of the packages, Al Qaeda in the Arabian Peninsula “is at the top of the list” of suspects, a U.S. official told Fox News.

Federal law enforcement officials said the suspicious device that resembled a toner cartridge was removed from the a flight in a distribution center at East Midlands Airport in the U.K.

Officials for FedEx said the company also confiscated a suspicious package in Dubai that was shipped from Yemen and is cooperating with the FBI.

A crew member aboard a UPS plane arriving to Philadelphia from Paris, France later notified authorities on approach about a suspicious package. The crew member described a possible radiological component to the package, the incident report said. The two occupants safely exited the aircraft after landing in a remote area of the airport.

A second UPS plane was isolated near the UPS terminal at the Philadelphia airport before take off, the report said.

A third UPS plane, which arrived at Newark Liberty Airport from East Midlands in the U.K., was investigated, but UPS says it was cleared and proceeded on to Louisville, KY.

Two UPS trucks in Brooklyn and Queens, N.Y., were also investigated and cleared, officials said.

Law enforcement officials also are investigating a suspicious packages in Portland, Maine. No word on whether that package has any links to UPS or Yemen.

“As an additional safety measure, FedEx embargoed all shipments originating from Yemen,”Maury Lane, spokesman for FedEx told Reuters.