Lets look at outsourcing
I do not think outsourcing in flight service (i.e flight attendants) would be as difficult as may be thought. Flight attendants do not required any advanced education, a vocation training program I think could create a large number of flight attendants quickly. If United had an outsourced contract including customer satisfaction service level agreements, it might force better service and would require United to manage FAs as a supplier which would have significant benefits. This means united management would have to monitor services and manage the process perhaps by having occasional outsourcing compliance audits and a formal customer service surveys and managment safety inspections.
I think united has many fine FAs but the fact of the matter is like many occupations they have to accept that their value in the marketplace has changed. A sound business plan could be constructed for outsourced flight attendants that any airline looking to relieve itself of a union contract could turn to. I have done this kind of work for other industries and see no reason it could not work here as well.
At any rate a thought for consideration.