An air intake system for an aircraft engine includes an air duct having an inlet port to provide fluid communication between the inlet port and the engine and a removable air filter assembly configured to interface with the inlet port of the air duct and a skin of the aircraft. The air filter assembly includes an air filter frame having an outer wall and an inner wall, the outer wall of the air filter frame forming an air filter slot. The air filter assembly also includes a bypass door forward of the air filter slot and an air filter insertable into the air filter slot. The bypass door is movable between a closed door position and an open door position, air flowing to the inlet port of the air duct via the air filter in the closed door position and bypassing the air filter in the open door position.