Apparently, there are two kinds of "cash" vouchers out there. One of them is called a "Travel Voucher", which is written out on that yellow stock with black carbon ("special service ticket"?). I got one of these in place of a free roundtrip when I was bumped off of a flight. The value of a "Travel Voucher" may ONLY be used towards the purchase of a US Airways TICKET.

The other kind of voucher is a "Transportation Voucher", which is printed on US Airways ticket stock (like the stuff on which your boarding cards are printed). These can be used like cash towards US Airways tickets and/or fees.

I had this explained to me when I tried to use part of the value of my "Travel Voucher" to pay the $50 fee for changing the city pairs on my Swiss award.

Hope that helps...