Group: United violated passengers' Bill of Rights

United Airlines held passengers on a grounded airplane at Washington's Dulles International Airport for seven hours last week, violating federal consumer protections implemented last year by the Department of Transportation, a group said Monday.

FlyersRights.org said the plane, United's Flight 973, sat on the tarmac for 3.5 hours and then returned to the gate for more. Flight attendants prohibited passengers from leaving the plane and did not provide everyone with water, two provisions of the 2010 DOT rules, the group said.

The rules ban delays longer than three hours, but only specifically once the plane has left the gate. FlyersRights.org said that should be changed.

"United Airlines violated the letter and intent of the DOT rule, and should be held accountable," the group said in a statement. "FlyersRights.org urges the DOT to modify the definition of tarmac time to include gate holds of longer than 30 minutes after the plane is fully loaded, and to continue tarmac time accumulation while passengers are on board during unscheduled gate returns."

The Department of Transportation has touted the new airline rules, releasing statistics showing the number of delays longer than three hours has dwindled since they were enacted.

Under the news rules, airlines can be fined $27,500 for each passenger that is stranded on a plane.