After years of complaints and forewarning about a federal plan to reroute airplane traffic in the Denver metro area, Centennial Airport has filed legal action over how much care the government is taking to determine the impacts the plan could have.

“We just feel there are some pieces to the puzzle that are missing and very important not only to the airport, but to the communities,” said Deborah Grigsby Smith, Centennial Airport spokeswoman. “We stand very strongly with our neighbors, and we’d like to have a complete picture. We’d like to have it before Metroplex implementation — not after.”

The airport is taking the Federal Aviation Administration to court over the agency’s NextGen Denver Metroplex project, which aims to optimize arrival and departure at local airports. That includes Denver International Airport, Centennial Airport and some others. An FAA study, called a draft environmental assessment, looked at impacts the project could have on noise, air quality, wildlife, and historic and cultural resources.

The proposed change in flight paths is expected to have “no significant impacts” on those aspects of the Denver metro area, according to the April 22 study.

That lack of potential effects means a more rigorous review, called an Environmental Impact Study, isn’t necessary before the plan is put into action, according to the FAA.

That’s one of the determinations and actions by the FAA at issue in Centennial Airport’s legal action, which is a petition for review in the U.S. Court of Appeals for the District of Columbia Circuit. In the June 19 legal filing, the Arapahoe County Public Airport Authority — the government body that oversees the airport — asked the court to review the FAA’s study, its determination that an EIS isn’t needed and its proposed changes in flight procedures.

When reached about the legal filing, agency spokesperson Allen Kenitzer said the FAA "does not comment on ongoing litigation."

The filing also requested a look at whether the FAA can carry out the Metroplex plan before completing studies required by the FAA Reauthorization Act of 2018, a law passed by Congress.

The recent law requires the FAA to study the agency’s “community involvement” practices regarding NextGen Metroplex projects; the effect of aircraft noise on communities; the relationship between noise and health impacts such as sleep disturbance and elevated blood pressure, as well as the effect on businesses located under certain flight paths; and whether 65 decibels and up remains an acceptable FAA standard for significant noise exposure, according to a June 5 letter from the airport to the FAA.

The airport’s executive director, Robert Olislagers, has said that the results of those studies could significantly impact the Metroplex project, as well as the FAA’s conclusion that it would cause no significant impacts to the metro area.

The airport has also argued that the FAA didn’t consider the impact of the part of flight that occurs below 3,000 feet above ground, and that leaves unclear how much communities could be affected. Littleton, Centennial, Cherry Hills Village, Lone Tree, Castle Rock and other nearby cities could experience notable effects, Olislagers has said, although it is unclear how much.

The FAA contends that most proposed flight paths in the Denver area closely follow what are being flown today.

Legal action has been initiated against the FAA regarding NextGen implementations in Phoenix, as well as in the Los Angeles area and the Baltimore-Washington, D.C., region, according to the airport’s letter.

The D.C. appeals court in the Centennial Airport case set July 22 and Aug. 5 as dates when certain documents must be submitted in the case.