Polish athlete Sebastian Szubski is escorted from court in St. John's, N.L., on Sunday. (CBC)

A 28-year-old Polish athlete is in custody in St. John's for a psychiatric assessment to see if he is fit to face trial on assault charges stemming from an incident on board a transatlantic flight.

Sebastian Szubski was arrested and charged early Saturday after the plane he was on from Halifax to London was diverted to St. John's.

Police said there had been a disturbance on the plane, during which a man was put in a headlock.

Szubski and his father were in Dartmouth, N.S., last week for the World Canoeing and Kayaking Championships. A canoeist, Szubski competed for Brazil at the 2004 Olympic Summer Games in Athens.

A psychiatrist who assessed Szubski over the weekend told the court on Sunday that he believes the man is ill, but that more time is needed to form an official opinion about his mental health.

Szubski was visibly distressed during his court appearance, breathing deeply and bending over to put his head between his knees, but told the judge that he was fine.

"I just want to go home with my father to Poland, to see my mother," he said.

He is scheduled to be back in court on Friday.