The invention discloses a system and a method for examining an aircraft. An X-ray source and a detector are respectively arranged at the upper part and the lower part of the body of the aircraft. X-ray beams which are produced by the X-ray source penetrate through the to-be-examined aircraft. The X-ray beams penetrating through the to-be-examined aircraft are received by the detector and converted to output signals, and an overlook transmittance image is generated in real time.