(My original booking for a 6:50 AM flight went pear-shaped when UA cancelled the flight - got paged just after the cabin door closed on my flight to ORD!)

Talked to the Airserv person inspecting Premier/Elite boarding passes at the entrance to the Premier Access security line adjacent to the Group 1 counter on the southwest end of Terminal 1/Concourse B. She said that the line opens at 4 am ("I think" were her words...). Other Premier Access security line at other end of Terminal 1/Concourse B, she was even less sure of.

FWIW, the Premier Access security line (Group 1 counters) @ around 7:45 AM Saturday was only about 20 people long = ~ 5 minute wait to get my boarding pass and driver's license inspected by TSA.

David