The problem is the actuarial
assumptions haven't been coming true especially the estimates on
investments of the pension f

Many of those assumptions were used by the unions to argue for their
massive benefits program. Supply and Demand work wonderfully. Putting a
union in there messes with that (almost by definition). W/O the union,
the airlines would have paid exactly what was necessary to get the
quality of employees they needed, and no more.

-Robert