If you stand at the very center of Renton Airport’s runway, and look north toward Mercer Island, you’d notice it perfectly aligns with Island Crest Way. Ryan Zulauf, airport manager, points out a V-shaped break in the trees, where the Island’s major thoroughfare runs North-to-South.

Standing at the northernmost tip, on the edge of Lake Washington, about 9,000 feet separate the tarmac from MI.

Runways are aligned with the prevailing wind direction and in the case of Renton Airport, that happens to also mean Island Crest Way.

“On arrival, aircraft must descend in altitude meaning that they come closer to the terrain on Mercer Island, especially given that the Island is substantially higher in elevation than the airport runway,” explains Zulauf. “So the aircraft is coming closer and closer to the ground as it’s lining up with the runway.”

Airplane traffic has been an ongoing issue on Mercer Island.

In 2013, there were 39 total noise complaints, 10 of them from Islanders. That’s significantly less than the 57 logged in 2012, of which 14 were from MI. Renton is a general aviation airport, serving everything from private planes to news choppers and the Boeing models at the neighboring factory. A runway stretches to the edge of Lake Washington and a map of flight routes in a single day in the airspace over MI reveals a knot of flight circuits. The map below is almost entirely obscured by the routes.

“The airport issue, I think for some people, it’s an issue that just will not go away, as long as the airport is there,” said Bob Brahm, a retired pilot who flew with Alaska Airlines until 2004 and served for several years on the Renton Airport Advisory Committee. He lives at the south end of the Island. “They’ve looked at problems and potential solutions and selected the best ones that make sense safety-wise.”

Though it’s been effectively mitigated through the years, complaints resurface every so often. There are many factors contributing to the noise level of an aircraft, ranging from its size and model to the type of landing. New technology has made it easier to mute noise. In 2017, Boeing’s new 737 MAX planes, built in Renton, will be delivered all over the world with a noise footprint much quieter than aircraft of a similar size.

While it’s hard to determine the source of the noise complaints without tracking them back to the exact time and date, airplanes are generally noisiest when taking off and at full-power.

Zulauf says noise might fluctuate depending on the type of activity at Renton airport. Generally Boeing uses the tarmac only for departures. Thirty-eight Boeing planes are made at the adjacent factory each month, a number that will grow to 42 next April. Airplanes leave the Renton factory for their home base, for instance to become a part of a commercial fleet. But recently, a few of the Boeing jets have landed over the Island.

“We’ve had some Boeing jets return during the month of December, which is not typical. It used to be zero and now we’ve had a few returns, which is just part of the occasional smoothing of the 737 production process,” he explains. “When we have those returns, a few have come in…over the Island.  And we’ve heard from neighbors wondering why this big airplane is flying down the center.”

Nancy LeVine, a resident on the north end, says the air traffic was most notable after several foggy days this fall. Weather conditions greatly impact flight patterns and LeVine began noticing that her dogs reacted to the planes like they would thunder or fireworks. She had to use a noise machine to camouflage the sound.

“I’ve been sitting outside watching and every three minutes, literally every two to three minutes a plane passes overhead. That’s not every day, but there have been days like that,” says LeVine, a photographer who also notes that working from home has made her more aware of the airport traffic. “They come in spurts. Sometimes I’ll wake up at 6 a.m. and it might go continually.”

Toward the end of a sunny Friday, two employees at the Renton Airport control tower overlook the tarmac issuing instructions almost constantly for minutes at a time. The space is decorated for the holidays with snowflake cutouts hanging from the ceiling and red ribbons along the staircases. On this particular day a crane obstructs the north end of the runway. The airport is dredging Lake Washington around its seaplane base through late December and because of it, airplanes are limited in their takeoffs and landings.

Historically, airplanes could only do straight approaches. For the last 15 years, Boeing jets have had the technology on board to do curved approaches in noise sensitive areas, says Zulauf.

“And yet we don’t have the procedures developed to allow aircraft to do this at the Renton Airport,” he explains.

To accommodate growing airline traffic, the FAA says airports must be open 24/7, much like I-405 or any other major arterial. The most recent available numbers indicate 96,000 annual operations. There is a direct number for noise complaints, all of which staff log, but mitigation is more complicated. As a federal airport, both the cities of Mercer Island and Renton aren’t at liberty to control the types of planes that fly in and out.

“We can have a discussion with the pilot, but, we don’t have the authority to do anything. It’s the pilot who is in command and FAA regulations don’t allow curfews on airports, or on aircraft since the passage of the federal Airport Noise and Capacity Act of 1990.”

In May of this year, the Puget Sound Regional Council (PSRC) wrapped its NextGen study, which highlighted areas of improvement for 13 busy airports in the region, of which Renton was one. Results ranged from how aircrafts approach the landing strip to safety procedures. For instance, the separation between the runway and taxiway is currently 300 feet. It would need to be 400 feet if Boeing’s 737 MAX models were designated as Renton Airport’s critical aircraft.

Stephen Kiehl, principal planner for PSRC also notes that there are 28 airports in four counties. Renton is hardly the only one responsible for air traffic. Auburn, SeaTac and Boeing field all contribute to the noise, as well as cargo planes from UPS.

“There’s a lot of activity in the air,” says Kiehl. “One of the things we’re trying to accomplish in our NextGen work…is to reduce congestion in the air space, improve efficiency and of course our number one goal is to enhance safety.”

Zulauf says the airport and advisory committee is still exploring its options before acting definitively. Additional steps, he says, need to take into account the surrounding community.

One proposed solution from the NextGen study would use RNP (Required Navigation Performance) procedures to the north, reducing noise by flying a curved path over the lake, instead of directly over Mercer Island. Aircraft would take two turns and then zip down the runway, reducing noise impacts, says Kiehl.

But, cautions Braum: “What seems intuitive—‘let’s change this, let’s change that’—isn’t…You can’t just change flight profiles. That makes it more dangerous for everybody and safety is paramount. Airplanes need room to take off and land…[Renton Airport] is very conscious about its noise imprint. And really, general aviation is an economic factor for this part, whether people like it or not.”

For more information about the PSRC NextGen study visit psrc.org. Renton Airport’s website is available at rentonwa.gov.