The Daily Mail said the couple were romping on a flight from Manchester on Thursday evening. A female passenger next to the couple asked to be moved as they removed some of their clothes and a woman straddled her partner in his seat.
The paper quotes another passenger who said that staff took no further action despite complaints about the drunken pair.
Other passengers filmed the couple and the paper has published pictures.
Ryanair told the Mail that it was “looking into this matter”, and said that passengers who behave in an unacceptable manner “may be liable for further sanctions”.
