Door close times are 10 minutes at all stations EXCEPT LAX, which is 15 minutes. If you’re not added to the standby list at D-15 at SFO, or (gasp) D-30, the GAs are being lazy or you can’t clear (like the SEA-PDX flights with 25 standbys for five seats). If you’re offloaded at D-15, it’s a pain to get back on, but they shouldn’t offload anyone until 10 minutes prior, provided you’re checked in. Once the flight is closed, they can’t put anyone else on. Obviously if it’s full and everyone is on, they can close it up early, but they can’t push more than five early.

This whole board the plane 50 minutes before departure (I’m talking about you, MCO station agents), is absolutely ridiculous.

A very sweet, long time GA explained this to me at LAX when I tried to sweet talk my way onto a flight at D-15 there.