A "black hole" approach was implicated. "Black holes" were implicated in the demise of several Boeing 727s in the early 1960s. As older, piston equipment was replaced by jets, the traditional noise, vibration and motion cues were lost. The term "black hole" comes from having a brightly lit airport surrounded by black terrain, such as fields or water. This contributes to a perceptive illusion that the airplane is higher than it is, and leads to the airplane flying into terrain, sometimes miles from the runway. See also "Controlled Flight into Terrain."