A gas turbine engine nacelle includes a first annular portion that is stationary and adapted for partially surrounding an engine core. The first annular portion includes a fore pylon connecting portion. A rail is coupled to the fore pylon connecting portion and extending in the aft direction from the first annular portion. A second annular portion, aft of the first annular portion and coupled to the rail, is movable along an engine core centerline between a closed position and at least one open position. The second annular portion is configured to engage with the first annular portion when the second annular portion is in the closed position, thereby providing access to the engine core. A guide pin extends forward from the second annular portion. A locking mechanism is disposed within the first annular portion for engaging the guide pin when the second annular portion is in the closed position.