A couple who had never met before are facing a federal investigation after they indulged in a sexual act mid-flight to the horror of fellow passengers.

The total strangers boarded the Delta flight from Los Angeles to Detroit on Sunday 29 October and were sat next to each other.

The 48-year-old Miami-bound woman and the 28-year-old Nashville-bound man then got friendlier than expected.

But passengers were then horrified to find that the pair were engaging in oral sex, mid-flight.

The pair were arrested on the plane and told to stay in their seats.

They were issued citations after the flight and the investigation was handed over to the FBI who may press charges against the duo.

Speaking to WDIV, one of the passengers said: "The act itself is inappropriate in a public space.

"There are children. There are families. There are seniors. These things should be respected."

Another said that if "people are willing to go so far as to disrespect themselves and disrespect you, something should be done."

The FBI have said that the incident is still under investigation, but the pair could be charged with as little as a misdemeanour or even a more serious felony.