Gold / Platinum / Chairman get a third bag checked free of charge but it is only up to 50 pounds. Only First gets you the allowance of 70 pounds. I traveled with lots of luggage last year for work so I became familiar with the rules.

It is ironic that technically you can check 150 pounds total but they won't let you check say a 40 pound bag and a 60 pound bag without paying overage on the 60 pound bag. I just started to take an extra pelican case so I was under 50 on three items because I was not always getting upgraded.