U.S. Airways cutting its pension program

[earlthesquirrel]

I've read on other sites that U.S. Airways is requesting to cut it's pension program. This will understandibly affect a great many people. Why have pilot unions negotiated defined benefit plans and not defined contribution plans? My understanding is that at Southwest they have a defined contribution plan into an account that the employee can direct but the company can't touch if the employee is vested. This seems a perfect solution to pilots losing their retirement when a company goes Chapt. 11 or 7.

thanks