A federal court has ordered the National Park Service and the Federal Aviation Administration to adopt limits on noisy air tours over 23 national parks, including Hale­akala and Hawai‘i Volcanoes national parks.

The Friday order came in response to a lawsuit by Hawaii Island Coalition Malama Pono and Public Employees for Environmental Responsibility, which argued the agencies were offering little relief from the noise being generated by air tours.

“For almost 20 years, the FAA and the NPS have allowed an airborne reign of terror to go unmitigated over park skies,” Paula Dinerstein, Public Employees for Environmental Responsibility general counsel, said in a statement.

In its ruling, the U.S. Court of Appeals of the District of Columbia chided the agencies for failing to fulfill the mandate of the National Park Air Tour Management Act of 2000, which required the FAA, in coordination with the National Park Service, to set limits on overflight numbers, timing and routes to protect park resources and the visitor experience.

The court called the effort by the federal agencies “underwhelming.”

The agencies were given two years to complete plans for all 23 national parks, and the court said it would monitor the effort’s progress and reserve final approval of the plans.

The Hawaii Helicopter Association said operators have invested in quiet aircraft and technologies over the past several decades and are working to ensure “responsible operations for both our residents and visitors.” The investment includes a digital tracking system that addresses several areas of concern to help with compliance with regulations, the organization said.

U.S. Rep. Ed Case, D-Hawaii, who has led efforts to regulate the air tour industry in the islands, said the federal court got it right when it concluded the FAA and Park Service failed to comply with the law over two decades.

“In that period the destruction of our national parks from virtually unregulated air tours has worsened exponentially,” Case said in a news release. “I expect the FAA and NPS to fully comply with the court’s order and will do all I can to assist.”

Last year saw more than 47,000 park overflights concentrated mostly over a dozen national parks, including Hawai‘i Volcanoes on Hawaii island and Haleakala on Maui, according to the Washington, D.C-based Public Employees for Environmental Responsibility.

A National Park Service report published in October said that of all the national parks, Hawai‘i Volcanoes is the one most affected by tour helicopter flights, with 8,333 flights in the prior year, or about 22 flights per day, 365 days per year.

That number had dropped to half as much as when the volcano was erupting. The same report indicated Haleakala National Park is the fourth most affected park, with 4,757 flights in the prior year.

“At that level of overflights, the peace, serenity and sanctity of our parks is destroyed and one of the core purposes of our parks is utterly defeated,” Case said.

“In addition to the complete degradation of the park experience, life in the surrounding communities over which the tour helicopters fly to access the parks is to many resident unbearable and the heightened safety risks are clear,” he said.

In its ruling, the court described the stalled management plan as the victim of a turf war between the FAA and the National Park Service, with both agencies unwilling to give up control in certain regulatory areas.

“Mandamus relief can’t make money grow on trees, but it can end an interagency turf war,” the order said.

The lawsuit had asked the court to order mandatory deadlines for adoption of air tour limits covering seven parks that account for more than half of the overflights: Hawai‘i Volcanoes, Haleakala, Glacier, Bryce Canyon and Great Smoky Mountains national parks; Lake Mead National Recreation Area; and Muir Woods National Monument.