US Airways Dividend Miles (Pre-FlightFund Merger) - How Early Before A Flight Can You Check In And Check Bags (official/unofficial?)

I am wondering how early you can check in at an airport for a flight. Does whether you have bags have an impact? I had heard, especially with bags, that you must check in 4 hours or less before the flight? Does anyone know if the computer literally prevents an agent from doing a check in in more than 4 hours until departure time? Like say its 4 hours and 30 minutes, etc? Do they have an over-ride that they can still check you in, and/or also check your bags? Idea is I want to drop my bags off, go to work for few hours, and then go back to airport with bpasses and all and just get on the plane more quickly.
Also on a related note I will be completing the second half of a domestic roundtrip to return to my home city, and then later the same day starting a new international ticket. So wondering when I check in at the first station if they could check me in for intl flight like 7 hours early.....also so as to get better place on standby list for O (envoy) class upgrade? In all the years of flying, have never really run in to yet wanting to check in so early.
I wish US would do telephone check in, now what could be more versatile and then just use the strip/bar code system like DL.

Four hours. At Pittsburgh they would not let me check-in more than four hours before a flight. USAirways phone confirmed this was their policy.

OTOH AA and CO both told me they don't care as long as it's the same day. I've checked in with CO as much as six hours early, and with AA as much as five hours early.

Well, the system can definitely check you in much earlier. This is especially true when you fly LAX-PHL-LGW. Your check-in in LA could be as much as 9-10 hours before the PHL-LGW flight.

Suppose you want to use the Club for one of it's marketed benefits - meetings.

You show up at the airport more than 4 hours early, go to the counter, tell them you have business meetings in the club prior to the flight. If your bag is too big for carry-on, you'd never get it past security and thus not be able to use the Club. Therefore, there should be provisions in certain cases to let you check in earlier than 4 hours.

If you have no bags, go to the club and ask the agents there to check you in. Policy or not, they can do it if there are good reasons. Getting on the upgrade standby list early is *not* a good reason (not that you said that's your goal)