Sept. 12, 2011 -- The FBI said today there was no "romantic" activity among passengers that led to F-16 fighter jets being scrambled to escort a Frontier Airlines flight into Detroit Sunday.
"At no time were there ever two people in the bathroom and the same time," the FBI said in a statement released Monday.
Local and federal law enforcement officials had told ABC News Sunday initial reports of "suspicious behavior" 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 behavior by several passengers. In that case, too, it turned out the passengers were making innocent, if frequent, trips to the restroom.
Federal air marshals aboard that plane were able to resolve the situation when the passengers complied with their instructions and the plane was landed safely. Again, three people were taken into custody, but were later released without charge.
Both incidents occurred while national security was on high-alert for the tenth anniversary of the Sept. 11, 2001 terror attacks. In that attack, four passenger planes were hijacked and used to kill nearly 3,000 Americans.
ABC News' Jason Ryan contributed to this report.