In my bumping experiences, it appears AA offers most generous voucher amounts and UA offers equivalent of $100 voucher per hour delayed.

Holidays are also the key times to expect bumping opportunities.

On Dec. 23, friends were traveling SFO-Belize on TACA. The flight was oversold and they were offered $600 in vouchers and night's hotel at SFO to go out biz class on AA through DWF the next morning. They took it.

In Dallas, AA was overbooked and they were offered $1500 to spend night in Dallas and go out biz on AA the following morning. They got to Belize two days late - and on Christmas - but they pocketed $2100 each in vouchers.

Same people booked SFO-CDG first Saturday of spring break on AA (paid for with their vouchers, of course ). They are offered $1100 to fly same flight the following day, plus hotel and food. Again, they took it.

On that same Saturday, my son and I were booked SFO-KOA on UA, first flight of the morning. They offered $400 in vouchers for anyone willing to take flight four hours later. I told the agent we'd take it if we could get biz class seats and she said, "No problem."

As we walked around the airport that day we paid attention to what flights were oversold. Morning flights on the first Saturday of spring break to OGG, KOA,IAD and Florida destinations seem to have high probability of being oversold.