On the international routes, the closest would be to threaten to wet-lease planes & crews to fly them or just drop the routes. No threats there ... yet.
Domestically, threaten to sell the slots at LGA & DCA. Already on the table. Threaten to farm out the rest of the domestic flying. Already doing that a step at a time - Mesa comes to mind.
In other words, been there and done that to a large degree. Didn't even get a tee-shirt.
Yes, the SAS tory is sad, but it is the typical divide and conquer tactic. SAS has been playing the diferent work groups against each other for years, now mind you, due to three different countries being part of it, there are three different Unions for most workgroups.
Lindegaard is playing hardball, but I am not sure he could actually replace say danish workers with swedish, while they do have the right to work in Denmark, it would do very little for relations between the two countries. And it could force the danes to seriously reconsider having anything to do with SAS.
including on that liquid threat, lets not forget the outsourcing of old mainline cities that are now called mainline express and the possibility of the commuter being sold.