Momade Jussab, 66, of Swinfield Close in Feltham, carried out the attack on a stranger on board a flight from Doha, Qatar, last September.
The 24-year-old victim fell asleep after the cabin lights were turned off but awoke to find Jussab sexually assaulting her.
When the plane landed she reported the incident to police.
Jussab was arrested and charged with one count of assault by penetration, and two counts of sexual assault.
On Friday, March 29, he was found guilty of the charges following a trial at Lewes Crown Court.
Detective Constable Kate Bailey said: “I would like to praise the victim for her courage to come forward and report her experience.
“This was a shocking incident and a crime which has a long-term impact on the victim and other victims like her.
“We were determined to get justice in this case, and we are pleased with the verdict.
“We encourage all victims of sexual offences to come forward and report their experience to the police.”
Jussab will be sentenced in May.
