More than nine years after a suit was first filed against the carrier Swift Transportation, over claims it cheated drivers out of compensation, it has been certified as a class action.

The move by an Arizona judge means litigation should proceed, involving potentially tens of thousands of truckers. It claims Swift used the Household Mover’s Guide, which on average produced mileage figures that are less than actual miles driven, to calculate mileage driven compensation, and did so without disclosing the practice. The result, the suit claims, is shorting driver compensation up to 10% at times.

The Arizona Superior Court has conditionally ruled the lawsuit is on behalf of one class consisting of owner operators who were given mileage-based compensation by Swift from March 2, 2001 onward. The second involves employee drivers of Swift who were paid by the mile from April 9, 2009 onward.

The case was earlier granted class action status in 2010, but Swift appealed, and that led to more legal wrangling by both sides, delaying the case.

Drivers that do not want to be a part of the lawsuit have until September 13, 2013 to ask to be excluded.