Delta Air Lines is being sued for allegedly hacking the e-mail account of a passenger rights advocate supporting legislation that would allow access to food, water and toilets during long delays on the tarmac.

Kathleen Hanni, executive director of Flyersrights.org, alleges Delta obtained sensitive emails and files and used the material in an attempt to derail the "Airline Passenger's Bill of Rights of 2009," of which four versions are pending before Congress.

The suit was filed on Tuesday in US District Court for the Southern District of Texas and seeks a minimum of US$11 million in damages.

Flyersrights.org, a nonprofit organisation founded in 2007, had been investigating surface delays in air travel. According to the suit, Hanni exchanged information with Frederick J. Foreman, who worked for Metron Aviation, which was hired by the US Federal Aviation Administration to study surface delays. The suit says Foreman provided information to Hanni with permission from Metron, including a report that fingered Delta as having excessive surface delays. Metron is also named in the suit.

During the correspondence, AOL informed Hanni that her emails, spreadsheets and lists of donors were being redirected to an unknown destination. Also, files on Hanni's computer became corrupted, the suit says. The hacking began in 2008 and continued through this year.

When contacted on Wednesday, Delta said: "The allegation that we would hack an individual's email is absurd."

Delta became angry about information given to Hanni that could aid the passage of the bills, the suit says. In an affidavit filed as part of the suit, Foreman said he was called into the office of James Gaughan, senior vice president and general manager of Metron, on 24 September.

Gaughan asked Foreman what information he had shared with Hanni, and Foreman said he sent Hanni information that was already public, according to the affidavit.

Foreman said in the affidavit that Gaughan showed him what appeared to be "hacked and stolen email communications" since the material involved the private email accounts of both himself and Hanni. The emails also included correspondence between Foreman and Gary Stoller of USA Today and Susan Stellin, a freelance reporter. Foreman was fired on 25 September, according to the affidavit.

If the bills are passed, airlines could lose as much as $40 million in revenue and spend much more to comply, the lawsuit contends. The bills would allow passengers to deplane if they've been delayed on the tarmac more than three hours. They'd also be entitled to clean air and access to medical treatment.