Years ago when flying BA LAX-LHR with my boss, someone well known in his business, while waiting in line to check in our bags a man in a suit approached us, told us just to leave our bags and follow him through an un-marked door. Down an innocuous hallway we went and into another unmarked door where there was a plush lounge full of celebrities. It was all a bit surreal.

Don't know if DL has anything like this, but I do know these types of "clubs" exist.