the first WTMD in the states was not in a airport. The idea to use a WTMD in a airport may have came from Alcatraz in S.F. There was a WTMD there to prevent the prisioners from stealing the utensils from the dining hall. The first walk thourgh's at the airport were the same ones logging camps used but placed upright. It was a tunnel type unit that looked like the sides were bulging out. World book encyclopedia's published in the eighty;s had a picture of the first kind of WTMD used in the airport.