Q: Two years ago, my wife and I volunteered to give up our seats on an overbooked United Airlines flight from Denver to New Orleans. We were issued vouchers that were good for two roundtrip tickets in the continental United States.

On Aug. 11, 2005, we redeemed the vouchers for tickets from New Orleans to Portland, Maine. We had arranged a 10-day trip touring the coastline of Maine during October.

Unfortunately, Hurricane Katrina hit New Orleans on Aug. 29, forcing us to evacuate the area. We knew that we would not be able to make the trip in October and canceled the flights to Portland with United.

I’m trying to get an extension on the vouchers, which would allow us to replace the trip we had to cancel. We are continuing to live the aftermath of Hurricane Katrina and a getaway would be most beneficial to our health.

Can you help?

— Orville Duggan, New Orleans

A: You knew that the vouchers expired when you accepted them from United. So when you failed to use them before their time ran out, the terms were clear: They’re lost.

But United, like many other airlines, bent its rules after Hurricane Katrina. For example, it issued refunds for flights canceled because of the storm — even for nonrefundable tickets. And it allowed many other passengers who were affected by the hurricane to rebook their flights without paying a fee.

So I think your request for an extension is reasonable, given what happened to you.

The next time you’re offered airline vouchers, consider your response carefully. The redemption rates for airline certificates are low, according to analysts. To me, that suggests that either the airline scrip is hard to use or that people forget they have it.

Either way, I think vouchers are a better deal for the airline than they are for passengers. The carrier gets to continue overbooking its flights — which, I should note, is a common industry practice — and then offer compensation that is of questionable value to its passengers.

There is probably a fairer way of handling an overbooking situation. I think airlines should offer credit that doesn’t expire and has real cash value, so that if it isn’t used, you’ll get your money back. But that is a matter for the airlines — or lawmakers — to consider.

I asked United about extending your vouchers, and it agreed that your circumstances were “unique” and sympathized with your situation. It offered you, and your wife, two travel certificates for $150 each, which can be used toward a future flight.