Former Los Angeles Clipper Darius Miles was busted yesterday for allegedly trying to bring a LOADED gun on an airplane in St. Louis ... and TMZ has obtained his mug shot.

Miles was arrested at Lambert-St. Louis International Airport ... where authorities claim he tried to take a loaded gun on a plane.

The 29-year-old former NBA player -- and St. Louis native -- was reportedly stopped after going through X-ray screening Wednesday afternoon.

Miles was booked on suspicion of unlawful use of a weapon.