Airline contract negotiations are under the Railway Labor Act of 1926.
The sole purpose of the RLA is to avoid disruptions in the nation's transportation system. The RLA requires that both parties maintain status quo during negotiations so no strikes, no lock-outs, no imposed new pay or work rules, and no work-to-rule campaigns.
The process to a strike, lockout, or other self-help measures is a long one that requires federal mediation, a proffer of binding arbitration, and the National Mediation Board must declare that the negotiations are at an impasse. At that point, a 30-day cooling off period is declared during which status quo is maintained. The mediator doesn't care if labor gets a fair contract or if management gets a reasonable one. His job is to prevent a disruption in service and eventually get an agreement. Neither labor nor management has control over when an impasse will be declared and the cooling off period begins. A mediator will often put negotiations on the shelf, for an indeterminate amount of time, if he feels that the parties aren't negotiating. That is the mediator's hammer to encourage movement. Near the end of the 30-day cooling off period, the mediator will call the parties back into mediation and it is here that many agreements are reached.
During status quo, there are few things that labor can do to put pressure on management to negotiate. One is informational pickets, which we've seen recently. Another is a strike vote with a very strong showing. Management frequently seeks to delay and agreement because almost all agreements result in increased cost of labor.
It is what it is, not because it makes sense to negotiate in this fashion; but because this is what results from the requirements of the RLA.