An Atlanta attorney has filed a proposed class-action lawsuit alleging airlines worked together to raise air fares, joining dozens of other lawsuits around the country.

The suits followed an investigation launched by the U.S. Department of Justice into possible unlawful coordination by some airlines.

The Atlanta suit, filed by attorney David Bain on behalf of a Massachusetts flier, names Delta, American, Southwest and United airlines as defendants.

In a written statement Tuesday, Delta spokesman Trebor Banstetter said: “The assertion that our success is due to anything more than the hard work of our people is not only ridiculous, it is offensive. While we are cooperating with the inquiry, the simple fact is that Delta has not engaged in any illegal behavior.”

In the lawsuit filed in the Northern District of Georgia and assigned to Judge Amy Totenberg, Massachusetts resident and Delta customer Martin Pomeroy alleges the four airlines conspired “to fix, raise, maintain, or stabilize prices of airline tickets” by constraining flight capacity and limiting access to fare information, among other means.

It also alleges airline tickets were maintained at “artificially high” levels, that passengers “were required to pay more for domestic airline tickets than they would have paid in a competitive marketplace ” and that they were “deprived of the benefits of free, open and unrestricted competition in the market for domestic airline tickets.”

The amount of the alleged injury has not been determined.

Attorneys who have filed suits in other states also have filed motions to consolidate cases across their country before a single judge in their jurisdiction. The goal is a class-action case that would likely include millions of fliers, but a judge would first have to certify class-action status.

A similar case in the 1990s, also spawned by reports of a Justice Department probe into industry pricing practices, was consolidated in Atlanta. It eventually was settled with members of the class eligible for discount coupons.