F-16 Falcon fighter jets escorted two U.S. domestic flights after crews reported passengers behaved suspiciously on board, U.S. media said on Monday. Law enforcement authorities in New York and Washington are on high alert against what was called by the authorities a \"credible but unconfirmed\" terror threat to the United States a decade after 9/11 terrorist attacks, which killed 3,000 people. Two jets shadowed the American Airlines Flight 34 from Los Angeles to New York. The scare was apparently caused by three passengers, who had locked themselves in the bathroom and were \"not compliant,\" NBC New York said, citing security officials. The passengers, who were reportedly drunk, remained in the lavatory during the landing. In another similar incident, an unknown number of F-16s was sent to escort Frontier Airlines flight 623 from Denver to Detroit, CNN said.The crew reported that two passengers acted oddly: one spent about 20 minutes in a restroom in the back of the aircraft, while the other waited in a forward galley before using the restroom for the same period. The passengers were taken into custody upon their arrival to Detroit, but no arrests were made.A bomb scare took place in the Kansas City International Airport, where an airport terminal was closed and evacuated and a bomb squad was brought in after a passenger refused to cooperate and open his bag at a security check.The squad used water hoses to inspect the passenger\'s luggage, but no explosives were found.