I've enjoyed a delicious Bloody Mary with that distinctive Delta flavor as early as 5:30 a.m. on the ground in F at BWI (local first call in the bars in Maryland varies by county but is usually 6 a.m.).

As for the Sky Clubs, I learned that the ones in JFK can't start serving until 8 a.m. In quite a few places on Sunday, you can't get a drink until noon (ATL and DTW are like this; I think EWR is too).