Is the airline industry having a change of heart about the way it lets you spend your frequent-flier miles? After years of making mileage redemption difficult by limiting seats and adding steep fees for “free” tickets, the first signs are now emerging of some carriers’ realization that those policies may be backfiring.

Not only have they alienated customers, but they appear to have weighed heavily on the airlines’ books, in which unused miles are a major liability. United Airlines, in particular, seems to really want you to burn your miles. After discounting domestic and European mileage tickets this year, it became the first major carrier last week to eliminate “close-in fees” of up to $100 for booking an “award” less than 21 days before travel…