DL didn't "let" Airtran/Valujet in the door. The ATL airport prevented DL from taking over a large number of the former EA gates. Following the collapse of EA in 1991, the ATL airport held onto EA's former gate leases as they tried to attract a replacement hub airline. TWA bit and assumed a number of EA's former gates and operated its short-lived hub from 1992-1994. Following the TW hub closure, Valujet jumped in.