AS does. Last December I got voice messages about my Christmas SEA-BUR trip and was told the flight was overbooked and asked for volunteers. I didn't volunteer because I had little kids but I was curious how high they sold the new tickets... The price must be way more than $400 voucher + around $150 one way... Otherwise they won't ask for volunteers days before the departure.. They don't expect enough people won't show up. They must earn quite a lot of money from rich people...