You can go to iddeals and try it for free, just go from AMS to where ever and it will give you numbers of seats available. they are suposed to have there own formulas to figure out seat numbers and seem to be closer than other sites when checking your own airline numbers and comparing.
It looks like you might be able to get a free trial on the asu site (the above link post mentions this-maybe no longer available).
On iddeals, just look AMS to PHX and it will probably show some US airway flights then compare numbers with wings.

Tony