Discovery, the unrestricted regular second-class ticket on Eurostar, is $248 round trip, compared with a standard economy class fare of $432 on British Airways.

Most airlines allow customers to be wait-listed only when they purchase unrestricted tickets, which are usually close to or at the full-fare price.

Lufthansa has cut off-peak fares on unrestricted, economy-class tickets in Germany up to 63 percent.

The round trip air fare is about $160 to $325 for a restricted ticket; an unrestricted ticket is $326 and up.

But he says he is aware that they eliminate critical freedom for business travelers who fly on unrestricted tickets.

In fact, Mr. Trippler said he was surprised that United did not announce a sale on unrestricted tickets just to attract more business travelers.

Full-fare, unrestricted tickets are most likely to be accepted.

No airline is likely to follow People in offering unrestricted cheap tickets.

(More expensive unrestricted tickets can generally be changed or canceled without penalty on any airline.)

It sells unrestricted one-way tickets on the domestic routes starting at $89, with the day of the week affecting prices by $10 to $30.