It's generally not a good business practice to alienate loyal customers, but United Airlines has done that to its frequent fliers who are general aviation pilots and aircraft owners. And United is paying the price.

More than 1,700 AOPA members (and counting) have written United in response to an e-mail campaign on June 27 that urged its frequent fliers to support FAA funding changes, including user fees. This is the second time in less than a month that United has offended loyal passengers, including their premier executive million mile fliers. (The first was an editorial in United Hemispheres, the company's in-flight magazine.)

Many vowed not only to stop flying with United but also to encourage their family, friends, and coworkers to boycott the airline as well. Some of those customers had flown with United on a weekly basis.

"As of today, all employees of our companies will be notified that United/Ted will be added to the list of 'no fly' airlines," one AOPA member wrote on Friday to Glenn Tilton, chairman, president, and CEO of UAL Corporation. "I am sure that is the considered consequence of your action, enjoy it!"  Read More
http://www.aopa.org/whatsnew/newsitems/2007/070702united.html