There is no set time. On a Sunday, it all depends on what time "the judge is willing to meet you at the court." Technically, they could file at 2300 if they can get a court to accept the filing at that hour. (The judge doesn't actually have to be there, but some poor clerk or other officer of the court must be there to receive the document.)
However, don't think that agreements with the unions will prevent bankruptcy. US Airways has about $200 or $250 million dollars between them and default on the ATSB-backed loans. The ATSB required that the company keep $725 million cash on hand. As of 30JUN, the company had $975 million cash on hand.
If the company makes the $110 million (I think that is the right amount) pension payment next Wednesday, that will instantly wipe out appox. half the "cushion." At the rate US Airways is burning cash (approx. $2 million/day last I saw), that would leave them with only about 50 days of operating cash. The only way to avoid the payment is to file for bankruptcy.
If a company has any hope of reorganizing in Ch. 11 and continuing as a going concern, that company can not wait until it is broke before seeking BK protection. If you have no operating cash, you can not put a/c in the air.
There is another possible scenario. The company could make the payment, not file for bankruptcy, and when they dropped below the ATSB cash minimum, dare the ATSB and the ATSB-backed creditors to call the loans. As Bush 41 might have said, "That wouldn't be prudent."
