Washington, Sept 13 : The FBI has confirmed that no "romantic" activity took place on board the Frontier Airlines flight that led to F-16 fighter jets being scrambled to escort it into Detroit on September 11.

"At no time were there ever two people in the bathroom and the same time," ABC News quoted the FBI as saying in a statement on September 12.

Local and federal law enforcement officials had said the initial reports of "suspicious behaviour" by multiple passengers that prompted the emergency call for F-16s was suspected of being a couple "making out" in the plane's lavatory mid-flight.

When the flight landed, the plane was taken to a remote area for security screening and three passengers were briefly taken into custody.

In the course of their investigation, the FBI found that one of the passengers, who felt sick, happened to get up and head to the bathroom at approximately the same time as another passenger. None of the three people taken into custody knew each other, the FBI said.

"After questioning and determining there was no threat, all were released without any charges being filed," the FBI said.

In a nearly identical incident the same day, an American Airlines flight from Los Angeles to New York's JFK got its own F-16 escort after the pilot of that flight also reported suspicious behaviour by several passengers.

In that case, too, it turned out the passengers were making innocent, if frequent, trips to the restroom. (ANI)