Passenger Nick Steffl said the man had been seated two rows in front of him near the back of the jet.
Steffl said he looked up from his audio book to see the man unclothed and yelling and moving forward.
The man approached the cockpit and Steffl said he thought it might be some sort of attack.
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Instead, the man turned and ran toward the back of the jet.
Steffl said he stood up and slapped the man in the face. Another passenger pinned the man's arms and help restrain him.
The flight landed safely about 45 minutes later.
The man was taken to hospital.
