Mental institution. One of the patients was running around, pretending to be a plane, so a doctor stopped him an asked what he's doing.

"I'm flying on a business trip to Thailand." said the loony and ran off. The doctor went to the guy's room and found the plane-man's roommate masturbating.

"What are you doing?" asked the doctor. The weirdo replied "Frank went to Thailand and I'm screwing his wife."