A federal appeals court Tuesday ruled in favor of the Federal Aviation Administration in its three-year battle with D.C. residents over noise from Reagan National Airport, handing the agency a significant victory as it moves forward with efforts to modernize the nation’s antiquated air traffic system.

A three-judge panel of the U.S. Court of Appeals for the District of Columbia Circuit said that while the residents’ argument had “some appeal,” their case would not be considered because they had missed the deadline for filing their complaint.

Residents of Georgetown, the Palisades and other Northwest Washington neighborhoods, who filed suit in 2015, maintained that they were not given adequate notice of changes to flight patterns that resulted in a significant increase in noise from planes taking off and landing at National.

In a unanimous decision, however, the judicial panel said the residents’ argument ran into “procedural and substantive obstacles.”

The judges noted that while the FAA’s efforts to notify Georgetown residents about the changes to flight paths “were hardly a model of sound agency practice,” the residents’ arguments ultimately did not qualify as one of those “ ‘rare cases’ in which reasonable grounds excuse the failure to timely file a petition for review.”

Under the law, the residents had 60 days from when the FAA finalized the new routes to file a petition for review challenging the changes. The residents, however, did not file their petition until more than a year later.

“Filing deadlines, replete throughout the United States Code, promote prompt and final judicial review of agency decisions and ensure the agencies and affected parties can proceed free from the uncertainty that an action may be undone at any time,” the judges wrote in their decision.

The panel’s ruling is significant because a different three-judge panel in August ruled in favor of Arizona residents in a dispute over flight paths in Phoenix. That case involved a similar issue of timing, but a majority of judges said the FAA’s handling of the transition was so bad that it overcame their concerns about when the petition was filed.

“Unfortunately the court did not reach the merits of the case and dismissed the petition for review as untimely,” said Richard Hinds, general counsel for the Citizens Association of Georgetown. “In this case the FAA made diligent efforts to ensure no one in D.C. was aware of the new flight path we challenged until it was an accomplished fact. We need to consider what if any steps we need to consider taking at this point, but pursuing our administrative petition with the FAA is one possible alternative to further litigation.”

D.C. Council member Jack Evans, who represents residents in Georgetown and other affected neighborhoods, called the decision “terribly disappointing.”

“This issue is way too important to decide on a procedural matter, and when judges do that, it’s a cop-out,” said Evans (D-Ward 2).

Even as they hailed the decision, FAA officials said they will continue to work with D.C. residents to address their concerns.

“Today’s court decision affirms the FAA met the requirements of the National Environmental Policy Act and considers final its northern departure routes from Reagan National Airport,” the FAA said in statement.

The decision could discourage more communities from suing. In Maryland, where residents have been grappling with similar noise issues involving National and Baltimore-Washington International Marshall airports, Gov. Larry Hogan (R) has directed Attorney General Brian E. Frosh (D) to sue the FAA.

It is not clear whether Maryland will follow through on its threat to sue, given Tuesday’s ruling. Neither Hogan nor Frosh’s office responded to requests for comment.

The FAA’s multibillion-dollar effort, known as NextGen, to modernize the air traffic control system is designed to replace the current system of radar navigation with a satellite-based one. The agency says the shift will make air travel safer and more efficient because planes will be able to fly more direct routes, but it also means planes will be concentrated over a smaller geographic area. The result has been a sharp uptick in noise complaints from residents on the ground.

“Families in our state and across the region continue to suffer from increased airplane noise since the FAA implemented the new NextGen flight plans,” said Sen. Chris Van Hollen (D-Md.). “The court’s ruling today failed to get at the heart of the matter — the impact of these changes on people living in our region. I will continue to work with all parties involved to ensure that the FAA gives additional consideration to cumulative noise impacts and works more cooperatively with local communities on flight path issues.”

A recent report by the Metropolitan Washington Airports Authority, which manages National and Dulles International, showed that the number of complaints has not only continued to grow but has involved a broader geographical region.

In all, airport officials logged 42,683 complaints about flights at National and Dulles in 2016, compared with just under 10,000 in 2015. The bulk of the complaints were about flights at National, and officials noted that more than half were filed by just two people.

In January, oral arguments before the appeals court panel focused on two areas — whether residents met the deadline for filing their protest and whether the FAA’s outreach efforts were adequate. The two sides differed on whether the changes to flight routes were fully implemented.

Though the judges gave no hint during oral arguments as to how they would rule, residents were optimistic, given the ruling in favor of Phoenix residents over changes to flight paths at Sky Harbor International Airport. That ruling required the FAA to revert to previous routes.