Twenty five years of measuring airline service quality or why is airline service quality only good when times are bad?

Airline service quality to many U.S. passengers may be the ultimate oxymoron based on stories, statistics and the perception that airlines help to foster. In reviewing data from the last 25 years from the Service Disquality Index (SDI) it appears that service quality in the U.S. is only met in times of economic distress or the after effects of terrorism. Due to recent actions mandated by the U.S. Department of Transportation, the chase for ancillary revenues and airlines perhaps finally practicing some constraint, major U.S. airlines are finally meeting minimum standards for service quality as reflected in recent SDI scores.