The Oregonian reports that 69-year-old Soren Muir Johnson of Eagle Point was arrested for investigation of reckless endangering.
Transportation Security Administration employees say he was told he couldn't carry his loaded weapon through a security checkpoint and that he should put it in his luggage instead.
They say that they watched as he disregarded that advice and instead dropped the .22-caliber pistol in an airport planter box on June 24.
Port of Portland spokesman Steve Johnson says police recovered the gun. Police say the man told them he hid the gun so he could retrieve it when he returned from his trip.