A door for aircraft is capable of blocking an aperture made in the aircraft. A framing of the door is connected to the fuselage by hinging means. The framing is mounted rotationally on the hinging means. The door is capable of taking two opposite stable positions, by 180.degree. rotation about hinging means. The door comprises means to lock the framing in either of the stable positions. A first face of the framing is fitted with an observation dome, a second face comprising an access hole to the dome.