Turns out, there was a celebrity onboard the Southwest Airlines flight that was delayed due to a co-pilot WITH A GUN ... and that celeb is UFC champ Tyron Woodley.
The reigning welterweight champion touched down at LAX after the incident at St. Louis Lambert International Airport early Wednesday morning.
TMZ broke the story ... one pilot was arrested after taking a loaded gun through security though witnesses had told us there were TWO pilots in handcuffs.
Woodley says he definitely saw TWO pilots.
Crazy morning for Woodley -- though he gives credit to Southwest for how they handled the incident.