I think the reality these days is that the NMB (National Mediation Board) isn't going to release anyone to strike anymore, unless it's a minor player like Spirit or something. I'm sure words like "critical to the national economy" and "putting 75,000 people out of work" would come up.

Thus, labor has no "big stick" to threaten management with - thus, management can string you along until you agree to what they want.