The main issue with labor and the airlines can be traced back to the early 90's when the airlines were loosing lots of money. In one year most airlines lost more money than they made in the past 50 plus years!!!!
In order to remain solvent, labor agreeded to major wage/work rules cuts--and to forgore raises. The expectation was that when the airlines returned to profitabiltiy, they would be paid back for their sacrafices.
The airlines turned the corner in 1995 and since 1997 have been making large profits. The unions have been negotiating since 1996 to regain what they lost and to share in some of the profits. The airlines stalled as long as they could and now are very worried with the downturn in the US economy (US business bookings are way off this year) they can't afford the wage demands being asked for by labor. The other complicating factor is United's generous package they gave to their pilots last year. All other unions are saying if United can afford this for their pilots, we should get the same percentage increase in our wages.
If the airlines were serious about avoiding future labor problems, they should study Southwest and adopt their profit sharring contracts it has with its employees.