Good points about airlines not leaving enough time, and the 1/2 hour standard is a good one. The reason I was asking, however, was that I wanted to know what the "cutoff time" was so that a gate agent can't hold it against me. I would hate to leave, say, 45 minutes and show up late, only to have a gate agent refuse to put me on the next flight because a legal connection for that airport was 50 minutes. Or conversely, after missing a connection the gate agent couldn't harass me for not leaving enough time if I could show that it was at or more than the minimum.