Originally Posted by
Antipode
If they're legal connections and you miss it because of delays, either in arriving or clearing immigration/security, they should accommodate you on another flight. That said, there is some risk here that you might be delayed a long time if later flights that day are full and they can't rebook you until a much later flight, so it's better to avoid the situation altogether if you really think it's impossible.
Bingo. UA sold us a 38 minute connection in SFO. We arrived 45 minutes after our connection had departed. It was the last flight of the night and there was only space the next afternoon. All earlier flights were sold out. UA moved us to a morning AS flight by request, but other passengers were not so lucky.