Some airlines admit they do pay more attention to consumer complaints if travelers send them to the DOT, which categorizes and tallies complaints and publishes monthly rankings of airline performance.
The DOT says it sometimes uses complaint data in enforcement actions against airlines and in rule-making decisions — a history of lots of complaints can work against an airline. The agency also points out trends with airlines hoping to pressure change.
In case you need to write a nasty email, here is the information you should include. Seems this technique could be used in other complaints to other businesses as well. CC the appropriate regulatory agency and Better Business Bureau in all of your complaint emails.