The 62-year-old star, who was travelling with fellow actor Baer, boarded a flight from Paris, France to Dublin, Ireland but was caught short when it was delayed on the runway.
He was told by the cabin crew that passengers were not allowed to visit the bathroom until after take-off - so he urinated in an empty bottle towards the rear of the plane. Urine splashed onto the floor, prompting the plane's pilot to taxi back to the terminal so the aircraft could be cleaned and the flight was delayed for a further two hours.
Baer has addressed the incident, insisting his friend is full of remorse for his actions but was unable to avoid the drama because of health problems.
In a statement, Baer says, ""Gerard is very sorry for what happened. He wanted to go to the toilet but he was forbidden because we were about to take off, so he was forced to do it on the plane in front of everybody. I found the solution by passing him a mini Evian water bottle, but it was too small and overflowed.
""He has prostate problems and it was very worrying and humiliating for him. He was also stone-cold sober at the time. This is not the way he usually behaves.""