Originally Posted by
warbo
Yes that's correct. If you use a voucher to buy a ticket, the voucher has then been used, and has no further value. By not flying, you have forfeited the voucher. It's normal practice, operated by most US based carriers.
I wouldn't say it's normal.
UA bump vouchers retain in the value of the ticket. If it's a $500 ticket, and a $300 voucher, the ticket still shows $500 value, paid for with voucher, and add-collect of $200. Change the ticket, it's still a $500 ticket.
CO and NW do the same thing as UA. Their bump vouchers' value stay within the ticket value, and an add-collect is charged for any difference.