The pilots would argue they're free to strike, and the airline would argue they legally couldn't. It's unclear. But the pilots are satisfied they could legally strike. And if they can't, they may do it anyway.
They can't survive a strike by the pilots for more than 24 hours.
A lengthy strike by the pilots ? probably anything over 30 days ? would be a disaster. I don't think the pilots would strike with the intention of putting Northwest out of business. Miscalculation. That's the problem.