Sick of paying fees to check your bags at the airport? Here’s some good news for you. A judge has ruled that a class action lawsuit against Delta Air Lines and AirTran Airways over baggage fees can continue.

The baggage fee class action lawsuit was filed in 2009, when customers sued the airlines for conspiring together to charge passengers for a first checked bag. The class action lawsuit alleged that AirTran’s chief executive told Delta, the current industry leader, that it would initiate a baggage fee if Delta did it first. Delta announced in November 2008 that, effective December 2008, it would start charging a $15 fee to check a first bag. Delta currently charges $23 to $25 for a first checked bag, depending on if its checked online or at the airport, and AirTran charges $15 for a first bag.

The August 2 ruling dismissed the plaintiffs’ original claims that Delta and AirTran attempted to monopolize the market through the conspiracy, but did rule that their claim alleging conspiracy should proceed. The judge noted that even though the two carriers are rivals in the Atlanta market, Delta “has consistently matched” AirTran’s low prices, including routes they share from Hartsfield-Jackson International Airport, where they both have hubs.

“Because the allegations in Plaintiffs’ complaint contain sufficient factual specificity to establish an unlawful conspiracy, dismissal would be improper,” the judge said in the ruling.

The judge added, however, that Delta had an explanation for the baggage fees that was “potentially legitimate and lawful.” Delta argued that it imposed the first-bag fee after it’s October 2008 merger with partner Northwest Airlines, which already charged a fee.

A Delta spokesman declined to comment on the ruling, other than to say, “It is notable that the decision recognizes that the harmonization of Delta and Northwest policies, as a result of the merger, would be a valid business justification for Delta’s action in adjusting its baggage fees.”

A footnote in the judge’s ruling noted that the two airlines’ conduct is currently being investigated by the Antitrust Division of the United States Department of Justice.

A copy of the Delta/AirTran Baggage Fee Conspiracy Class Action Lawsuit can be read here.