I have been able to book 30 minute connections on DL.com for as long as I have been a medallion. I have recently run into a problem though... I recently tried to change an itin which I was able to book online without a problem to another day. Note, all flights and routings are the same. I just wanted to move the trip up one week. I could not make the change online for some reason and when I called SMS to make the change, they would not do it becuase my 37 minute connection was illegal. I tried to fight because the website allowed me to book it but SMS said that ATL is now a 50-55 minute requirement based on the gate to gate transfer?! This does not make since as the flight would be an E to either C or D connection (LAX-ATL 777 connect to ASA). I have made this connection in 15 minutes before... much less 50-55! Ironically, the website still allows 30 minute connections... FWIW, If you have a tight connection, book it on the web as you could run into unforeseen issues with an agent.