ATSB loans are a subsidy.
Ch 11 does not remove the management whom caused the problem in the first place.
Court orders protectively reduce rates for employees, loans, aircraft etc that the non Ch11 company cannot do - effectively doing the job of reducing cost base when economically that company would have gone bust to allow for the entrepreneurial churn in the market that is essential to a healthy capitalist system - UK administration does not allow for unilateral decrease in the finance charges for aircraft for example - the creditor can and will walk away if they are not able to collect enough cash, and the company will go under, for new economically viable companies to replace it.
UA was denied an extension the the ATSB loan, it was not denied the original request after 9/11.
Dumping pension onto the PBGC certainly is an indirect subsidy. It relieves US airlines of the burden of paying their pension dues. There is no equivalent over here, the airlines have to pay their pensions or extract the money from the employees like BA is trying to do
There is similar over here following public pressure and recent legislation to protect members of DB schemes, which is why the Pensions Regulator in the UK will fine companies massively if they fail to cover the shortfalls on their DB pension schemes within 10 years. Effectively you are right - the government will not allow anyone to dump the pension on the government, but if they were to go bust before that shortfall were covered, the same could happen as did happen with UA and the PBGC. As BA is economically viable, the government will never allow the shortfall to be dumped onto them - BA has a choice between massive fines and extracting some concessions from staff.