A near-collision in midair last year prompted the Federal Aviation Administration to quietly change its takeoff procedures to route more flights -- and noise -- over south Minneapolis neighborhoods outside the official noise zone for Minneapolis-St. Paul International Airport.

The pattern is likely to be permanent.

For several months, neighbors and public officials have been frustrated at their inability to get an explanation for the increased noise or a prediction as to how long it will last. The FAA had cited wind conditions and airline scheduling, but residents were skeptical that those factors fully explained the prolonged increase in noise.

"There's clearly something going on, and nobody's 'fessing up to the neighborhoods what it is and why it is," state Rep. Jim Davnie, a DFLer who represents some of the area, said last week. "I've been in office 11 years, this is the first time that airport noise has come up as an issue."

The FAA confirmed Wednesday that the near-crash of a passenger jet and a cargo plane last September prompted the new procedure to improve safety.

"We had a previous procedure ... that we no longer use," FAA spokeswoman Elizabeth Isham Cory said. "It was discontinued after an operational error."

The noise you hear

Relatively isolated from airplane noise in past years, the Keewaydin and Ericsson neighborhoods have experienced a sharp and sustained rise in air traffic, according to the Metropolitan Airports Commission. Departures rose 25 percent this year over the same period in 2010.

"Plane after plane after plane" is how Candace McCown describes it. "I've been here eight years, and this is the first time it's affected us being outside or with our windows open. It's louder than it's ever been."

Keewaydin and Ericsson remain relatively quiet compared with some other neighborhoods in south and southwestern Minneapolis and parts of Richfield and Bloomington. One noise monitor in Ericsson shows it had less than half the excessive decibel level in August as the noisiest locations.

But for that area and the adjacent Standish neighborhood, the 1,501 excessive noise "departures" recorded last month at the Ericsson monitor represent a 47 percent increase over August 2010.

"We noticed it this spring," McCown said. "Our neighbors like to sit out in their yards and talk to each other. We've had to quit talking from 7 at night till 11."

Excessive noise levels increased 42 percent in April and May over the same months in 2010.

The pattern began even before residents spent much time outside or had windows open to notice. Noise increased more than 55 percent in January, February and March.

The noise stemmed from an increase in flights on parallel runways 30L and 30R, from 16,056 to 20,068 from last year to this year. Other neighborhoods saw no significant change in flights from the runways.

The increase may have drawn even more attention from residents because it occurred after a sharp decline in flights over the area in 2010 from the two runways.

Those parallel runways handle most takeoffs. Over the years flights departing 30L to head north would fly northwest for a while before making a northerly turn to avoid crossing in front of flights leaving 30R.

But the procedure sometimes caused problems.

What led to the change

A US Airways Airbus with 90 passengers and a Bemidji Aviation cargo plane were departing from 30L and 30R on Sept. 16, 2010. Two controllers instructed them to turn after takeoffs. The Airbus turned, but the cargo turboprop continued flying straight. The jet's collision avoidance alarm went off, and the pilot took evasive action. Less than 50 feet separated the planes.

The near-collision was among 21 operational errors at MSP from 2007 through 2010. A Star Tribune analysis showed the number of errors exceeded those at airports in Los Angeles, Detroit, Denver and Phoenix -- each of which logged more arrivals and departures.

After the incident, the FAA changed its procedure to avoid having planes cross fly routes.

"We felt it was safe at the time; now we feel it is safer to depart ... without any crossover," Cory said.

More northbound planes are now departing northwest on 30R and making a quick right turn -- over Keewaydin and Ericsson -- instead of making that turn about a mile west of the neighborhood.

Chad Leqve, the Metropolitan Airports Commission official in charge of managing noise, said he was unsure of all the factors contributing to the flights over the neighborhoods before he met with an FAA official this week.

That's when he and City Council Member Sandy Colvin Roy, who represents the area, said they were told about the change in procedure.

"It kind of came out of the blue," Colvin Roy recalled. "He said this is definitely a permanent change."

Pat Doyle • 612-673-4504