A group of airline passengers is seeking to block the proposed merger between Northwest Airlines Corp. and Delta Air Lines.

The group has filed a federal lawsuit in San Francisco arguing the proposed $3.9 billion merger between Eagan-based Northwest (NYSE: NWA) and Atlanta-based Delta (NYSE: DAL) would result in an illegal monopoly.

The suit, filed by the 28 passengers, alleges that the merger would result in higher ticket prices and diminished service. It also alleges that the new company would control 24 percent of domestic flights, thus reducing competition.

The news comes after U.S. Rep. James Oberstar, a Minnesota Democrat and chairman of the House Transportation Committee, called on the Justice Department last week to reject the proposed merger. He asked the agency to examine the deal in order to determine if would force other carriers to merge, resulting in raised fares and less service for consumers.

"This lawsuit is frivolous," Delta said in a prepared statement. "The Northwest-Delta merger is pro-competitive and pro-consumer because our networks have little overlap. The end-to-end combination of these two carriers enhances, not diminishes, consumer preference and choice. The DOJ is reviewing our case and we are highly confident this deal will be approved by year-end."

Delta Air Lines (NYSE: DAL) is the second largest carrier at Jacksonville International Airport in terms of both flights and passengers.