Join Date: May 2005
Location: various cities in the USofA: NYC, BWI, IAH, ORD, CVG, NYC
Programs: Former UA 1K, National Exec. Elite
Posts: 5,485
The CheckIn button for flights appears before one can actually checkin for the flight.
The button shows up exactly 24 hours before scheduled departure (pretty much to the second.) However, checkin, either with the button or by entering the PNR manually, does not work until about 1-3 minutes later. During this time I get an error message about having an invalid reservation/eticket (something like that).
I assume this has something to do with the EUAs being processed.