For the first 40 years of commercial aviation, planes were boarded much like trains had been, with no special security. Well into the 1960s, designers of airports still thought they would function like big train stations had, with passengers all waiting in a Great Hall until the gate was announced, and it took some time to adjust to passengers’ preference to instead wait at the gate to board. As late as the 1970s, you could just walk onto an Eastern Shuttle (LaGuardia to Washington National), sit down, and buy a ticket from the flight attendant when she came around.

In response to the first bombs and hijackings, airlines began screening with metal detectors in 1969, but it didn’t become a universal requirement until 1972. Airlines hired their own security contractors to do the screening, and any photographer can tell you they weren’t always fastidious about following FAA regulations (on hand-screening of film, for example). After 9/11, of course, the responsibility shifted to TSA and rules became much more uniform.

Here’s a timeline of air security