In the automotive industry, a gull-wing door, also known as a falcon-wing door or an up-door, is a car door that is hinged at the roof rather than the side, as pioneered by Mercedes-Benz 300 SL, first as a race car in 1952 (W194), and then as a production sports car in 1954. Opening upwards, the doors evoke the image of a seagull's wings. In French, they are (butterfly doors). The papillon door was designed by Jean Bugatti for the 1939 Type 64, 14 years before Mercedes-Benz produced its similar, famous 300 SL gullwing door. The papillon door is a precursor to the gullwing door, and is slightly different in its architecture, but is often overlooked when discussing gull-wing design. Conventional car doors are typically hinged at the front-facing edge of the door, with the door swinging outward horizontally. Apart from the Mercedes-Benz 300 SL of the mid-1950s, Mercedes-Benz SLS and the experimental Mercedes-Benz C111 of the early 1970s, the best-known examples of road-cars with gull-wing doors are the Bricklin SV-1 from the 1970s, the DMC DeLorean from the 1980s, and the Tesla Model X of the 2010s. Gull-wing doors have also been used in aircraft designs, such as the four-seat single-engine Socata TB series built in France. Practical considerations The design is a very practical one in a tight urban parking space. When properly designed and counterbalanced, they require little side-clearance to open (about 27.5 cm, or 11" in the DeLorean and allow much better entrance/egress than conventional doors. The most obvious downside to having gull-wing doors is that, were the car to roll over and come to rest on its roof, exit by the doors would be impossible, requiring a large windscreen opening to escape. The Mercedes SLS solved this problem by fitting explosive bolts in the hinges, that would blow up if the car rolled over. The Volvo YCC, a concept car designed by and for women, had gull-wing doors as part of its design. Gull-wing doors make it easier to lift a bag to store it behind the driver's seat, increase visibility over the driver's shoulder, and make it easier to get in and out of the car. The Tesla Model X, first introduced in 2015, has double-hinged gull-wing doors, called falcon-wing doors by Tesla. The Model X has several design considerations to make the doors more practical. Being double-hinged allows them to open with less