All of the above is true, however, if things change significantly (IE the number of writeups or sick calls exponentially increases), particularly company wide, then the courts can find the union in violation of labor law (slowdowns/stoppages) and impose significant fines. The key word is status quo. What was before the contract imposition, should continue with minor variances.

It's true that there is no indentured servitude, however unless all the pilot QUIT flat out, they are bound by various contractual and legal issues.