Three Wisconsin residents have filed a lawsuit against Delta, United, Southwest, and American airlines claiming they violated anti-trust laws. The plaintiffs are currently attempting to get their class certified.

In their complaint, the plaintiffs allege (in their only count) these airlines conspired to restrain trade and commerce in violation of the Sherman Act (15 U.S.C. §§ 1, 3) by artificially lowering the amount of airline flights thereby reducing competition within the industry. They explain that since 2008 the four major airlines have cut flights, raised fares, and have gained control of 80% of the market place. Fares have continuously increased despite a 34% drop in fuel prices, which are airlines single largest expense.

This lawsuit comes on the heels of the U.S. Department of Justice opening an investigation into “possible unlawful coordination” among major airlines’ plans to expand in a way to reduce competition and keep rates high. Several major airlines have announced they would limit growth in order to keep fares high to protect profit margins. However these statements were made in the context of preventing airline stock prices from declining further than they have in recent months.

Multiple similar lawsuits have been filed in major cities across the U.S. including New York, Chicago, San Francisco, Dallas, and Washington. The defendant airlines have released statements saying the lawsuits have no merit.

Read the complaint.