From airliners.net

Once the judge has accepted the Ch 11 petition - pretty much automatic, I believe - management has a 120-day period of exclusivity to restructure the business. There can be no hostile takeover offers. There can be no friendly takeover offers without approval of the judge and creditors' committee within that period. That 120-day period can be extended by the judge out to 18 months.

That's one of the reasons that U.S. Chapter 11 restructuring is so powerful in helping firms restructure, and why carriers like LATAM, Aeromexico, and SAS used U.S. courts. Once you let creditors and takeover specialists pick at the carcass there's quickly nothing left.