WASHINGTON - A New York-bound American Airlines flight landed safely Sunday at John F. Kennedy International Airport, after a security concern caused two military aircraft to escort the plane till its landing.

Flight 34, which departed from Los Angeles, California, notified the Transportation Security Administration (TSA) at about 3 pm that some passengers onboard the flight were "behaving suspiciously," the TSA said in a statement.

Two F-16 fighter jets were sent to escort the flight "out of an abundance of caution," according to the statement.

The airliner landed at New York's JFK airport shortly after 4 p m and the FBI has responded to the scene for interviews and investigations.

Three passengers onboard the flight locked themselves in the bathroom and refused to come out, local media reported. While the nature of the incident was unclear, some law enforcement officials said it was not believed to be a terror threat.

The airliner did not request escorts or extra security at JFK upon arrival, NBC New York quoted American Airlines spokeswoman Andrea Huguely as saying.

The incident occurred when the US was on heightened alert Sunday, the tenth anniversary of the September 11 terrorist attacks. A tip of potential terror plot to coincide with the anniversary was picked up Wednesday by US intelligence agencies, which said at least three individuals planned to launch a vehicle-borne attack against Washington DC or New York around the anniversary.

While intelligence officials have not yet confirmed the validity of the threat and could not identify the would-be attackers, security measures were significantly boosted in the two cities, which were at the center of the attacks a decade ago along with Shanksville, Pennsylvania. Terrorists hijacked passenger planes and crashed them into the three locations, killing nearly 3, 000 people.

www.allmycbs.com