As flight paths changed, residents of Boston; San Francisco; Culver City, Calif.; and Washington, D.C., sued the F.A.A. over the increase in noise. The City of Phoenix brought the first successful lawsuit and had the flight paths reversed in 2017. Phoenix Sky Harbor International Airport tallied fewer than 25 noise complaints a year from 2010-14. When flight paths were altered in 2014, that number jumped to over 2,500; in 2015, complaints increased to almost 12,000.

In 2018, Maryland challenged the F.A.A. over the noise from the changed flight paths to Baltimore-Washington International Airport and Ronald Reagan Washington National Airport . And in June, Los Angeles sued to invalidate the routes to Los Angeles International Airport; Culver City recently joined the suit.

In August, the Department of Transportation’s inspector general’s office released a report saying the agency’s NextGen plan fell short of expectations. It noted “community concerns about aircraft noise,” and said annual fuel savings were nearly half the minimum amount initially expected.

The F.A.A. said it was “committed to working with airport and community-sponsored round tables to understand and address concerns regarding noise from aviation.” It added, “In the event airspace changes are recommended, care must be taken to avoid simply shifting aircraft noise from one community to another and to ensure broad community buy-in for the proposed changes.” The system is now expected to be fully rolled out by 2021, to allow the F.A.A. to confer with communities it overlooked.

Although not designated a metroplex, the New York area is one of the most congested in the country for air traffic. Its three airports, Kennedy International, LaGuardia and Newark Liberty, have some NextGen features, and residents in nearby Nassau County and Queens in particular complain frequently about noise.

“A misconception about sound is as long we don’t hear it, it doesn’t matter if you hear it,” said Erica Walker, a postdoctoral researcher in the Boston University School of Public Health. She is monitoring sound levels in several Boston neighborhoods and in October began a yearlong sound study of flight paths in Chelsea , just outside the city, where the median household income is $51,000 . Residents tell her, “N o one is going to listen to us.”

Thanks to quieter engines and planes, fewer people are exposed to significant noise now than in the mid-1970s, falling to just over 400,000 now from about seven million, according to the F.A.A. The number of people flying has risen to one billion from 200 million in 1975.