> ## Content Index > Fetch the complete content index at: https://airport.mmalc.com/llms.txt > Use this file to discover other available public pages before exploring further. # Fewer than one departure in ten - URL: https://airport.mmalc.com/one-in-ten/ - Published: 2026-08-22T17:30:06.000Z - Updated: 2026-08-22T17:30:06.000Z - Author: mmalc Crawford *What Sonoma County's own records say — and don't say — about its aircraft-noise proposals* As soon as November, the Sonoma County Board of Supervisors is expected to consider two responses to aircraft noise over West County. Departures became concentrated there after the FAA introduced the RREHD ONE route in January 2024\. Routes like this are formal published procedures — a named sequence of turns, waypoints and minimum heights that the FAA must design, review and approve before pilots fly them. On August 20, the Aviation Commission recommended a reduced version of a voluntary Fly Quiet program and up to $270,000 for another round of route design. Noise complaints rose from 1,135 in 2023 to 29,895 in 2025\. They reached 32,581 in the first five months of 2026 alone. The question before the Board isn't whether these measures are better than nothing. It is what they would deliver, when they would deliver it and what conditions they should be compared with. The county's own documents — especially the signed minutes of the April 16 Aviation Commission meeting — provide some answers but leave others open. ## Fly Quiet is aimed mainly at traffic that is not the subject of the complaints In the April minutes, Cignus, the county's aviation consultant, divides flights into two groups. Flights operating under instrument flight rules (IFR) follow fixed, protected routes. This group includes the RREHD ONE departures and accounts for an estimated 16,500 flights a year. The minutes compare these flights to trains on rails. Flights operating under visual flight rules (VFR), including many private and training flights, choose their own paths. The minutes say the Fly Quiet program will address VFR traffic. For IFR traffic, the recommendation was to formalize Fly Quiet "where possible." In practice, the published route and air traffic control instructions would take priority. The airport manager has also said that Fly Quiet is separate from any change to departure routes. The program presented in August had seven parts. The Commission recommended four: voluntary quiet-hours guidance, airline noise scorecards, a community noise roundtable, and expanded online flight tracking and noise estimates. Two of the parts not carried forward were agreements with aircraft operators and daytime noise-reduction practices. Published reports don't separately identify the third part that was dropped. What remains is measurement, scoring and consultation. What was set aside includes the part that would have asked operators to make a commitment, as well as the only part aimed specifically at daytime practices. Yet the same minutes say flight activity peaks from 7 a.m. through the afternoon and into the early evening. The scoring system is worth a closer look. Airlines would be graded every three months on minimizing nighttime flights (30%), following "good neighbor" departure practices (25%), track adherence, meaning how closely they follow the published route (20%), continuous descent operations, meaning descending steadily rather than levelling off in stages (20%), and use of quieter aircraft (5%). No public document says which track airlines would be expected to follow. If it's the route published at the time, then a fifth of the score would reward airlines for following that route precisely. ## The waypoint altitude change affects fewer than one departure in ten RREHD2, the replacement route submitted to the FAA earlier this year, sets a minimum altitude at a point on the route called RREHD. On the county's own numbers, more than nine departures in ten are likely already at or above it. So the new minimum affects only the small minority now flying lower than the rest. This part of the redesign would bring those flights up to a height that more than 90% already reach. For the great majority, this minimum altitude changes nothing. That conclusion comes from the April minutes. They record a commissioner confirming that the short-term change deals with unusually low flights because more than 90% of aircraft are likely already at or above the proposed minimum. The minutes say the wider redesign would also make routes more predictable and raise aircraft over affected communities. But the public record supplies no numbers: it doesn't say how much higher aircraft would fly, which communities would benefit or how many departures would be affected. The only figure given is the range discussed in the next section. ## The advertised reduction doesn't say what is being measured The same minutes record expected noise reductions of 3.2% to 12%. They don't say what measure of noise would fall or how the percentages were calculated. The next line gives "1.5" as the point at which a difference can start to be heard, apparently referring to decibels. A percentage means little until the thing being measured is named. A 12% reduction in sound energy isn't the same as a 12% reduction in the noise from one flight, the number of people in a high-noise area or the number of complaints. And if the percentage applies to decibels, it's especially unclear. Decibels compress a huge range of sound into a small range of numbers, so a percentage of a decibel reading doesn't correspond to any fixed change in sound. The figures may be perfectly valid. The public record simply doesn't say what they mean. ## The consultant's first recommendation was to reinstate CHRLY8 The April minutes list Cignus's recommendations in this order, with estimated timelines: - Ask the FAA to restore CHRLY8 as the main departure route until a new RREHD route is approved: four to six months. The minutes say the FAA isn't expected to approve this permanently because CHRLY8 doesn't use its newer navigation technology. - Formalize Fly Quiet for VFR traffic, and where possible IFR: two to three months. - Complete the redesigned RREHD route for FAA review and rollout, without changing the links to the routes that follow it: twelve to sixteen months. The minutes say this would make FAA approval easier because it would avoid extensive training for pilots and air traffic controllers. - Complete and submit redesigned arrival routes: twelve to sixteen months. - Develop alternatives that change the departure path while preserving its links to later routes: thirty-six to forty-eight months for FAA review. This option would require controller training and might require a fuller environmental review. Of these, the second reached the Board in August in reduced form, along with another route-design project. The first — restoring CHRLY8 for now — doesn't appear among the August recommendations. The record doesn't show whether the county has asked the FAA for it in some other way. Among the permanent options, moving the departure path would take the longest and might require a fuller environmental review than RREHD ONE received. The FAA approved RREHD ONE through a "categorical exclusion." This allowed the agency to proceed without preparing the more detailed studies known as an Environmental Assessment or Environmental Impact Statement. The FAA's declaration said there were no unusual circumstances that called for further review. The one quick measure that would restore something close to the pre-2024 route is offered only as a temporary fix, and the FAA is expected to reject it as a permanent answer. That's an expectation about what the FAA prefers, not a finding that restoration is impossible. It hasn't been tested. ## Traffic growth can erode the reduction before it is delivered Airline arrivals and departures at the airport rose 15.4% year to date, to 7,528. That figure covers arrivals as well as departures across the airport. It can't simply be treated as the growth rate for RREHD ONE departures. But it illustrates the scale of the problem. Measures of noise over time add up the sound energy from each flight. Suppose departures over one corridor rose by the same 15.4%, while the types of aircraft and times of day stayed about the same. If those departures were the main source of aircraft noise there, the total exposure would rise by about 0.6 decibels. If traffic kept growing at that rate each year, it would add 1.5 decibels in roughly 2.4 years. The April minutes identify 1.5 decibels as roughly the point at which people begin to notice a change. The FAA's review of RREHD2 is expected to take twelve to sixteen months. The consultant expects FAA review of the later "phase 3" work to take twenty-four to thirty-six months. That creates an uncomfortable race: traffic growth could eat into the benefit before a revised route is even in place. This matters in another way. Not every noise complaint is about a changed route. Even when routes stay the same, more flights can mean more complaints. Nothing in the proposals before the Board addresses the number of flights. A redesigned departure route changes where aircraft fly, not how many fly. Routes are mainly an FAA matter. The number of flights is partly a county question about airport capacity and growth. The two problems have different answers, and treating them as one makes both harder to address. Two sets of federal rules limit what the county can do about flight numbers. By accepting federal airport money, the county promises to keep the airport open to aviation users on reasonable and equal terms. A federal law called the Airport Noise and Capacity Act also requires a demanding review before local officials can restrict access by most modern aircraft. Together, these rules make it difficult to refuse or limit airline service once the airport has room for it. Neither set of rules, by itself, requires the county to pursue every possible airport expansion. That makes decisions to add capacity more important, not less. The clearest time to weigh the effects of growth is before that capacity has been built and committed. ## The benchmark should be 2023, not RREHD ONE RREHD ONE was published in January 2024\. Departures became concentrated over West County after that. This isn't a long-standing problem to be reduced a little at a time. It is the change that produced the complaints. A measure could reduce noise compared with RREHD ONE while leaving most of a burden that didn't exist before 2024\. The right comparison is therefore with conditions in 2023, before RREHD ONE. That comparison should include the number of flights overhead, their paths and heights, and the noise from individual flights at selected West County locations. Whether the old pattern can be restored is a separate question. There may be real safety or airspace limits. But the county's own consultant recommended bringing back CHRLY8 as a temporary measure. That suggests a meaningfully different route is possible in the near term. Three weeks of changed routing during this summer's Bohemian Grove encampment showed the same thing in practice, at least while the airport tower was open. If the FAA can show that restoring the previous arrangement isn't practical, the next step is to discuss the least harmful alternative. That discussion shouldn't begin by accepting most of a burden introduced in 2024. ## Four questions the Board needs answered before voting The public record therefore leaves four basic questions unanswered: 1. What share of departures would the RREHD2 altitude change affect, and what improvement is expected for aircraft already meeting the proposed minimum? 2. What do the 3.2% to 12% figures measure, and how were they derived? 3. What is the expected first-year cost of the four recommended Fly Quiet components, and does the $98,000 annual ongoing estimate still apply now that the scope has been reduced? The four carry contract caps of $80,000, while the flight-tracking element alone was budgeted at $45,000 in the original proposal. 4. Is the $270,000 phase 3 exercise the longer-horizon option Cignus described in April — the one requiring controller training and potentially environmental review — or a separate piece of work? These questions don't require anyone to decide in advance whether Fly Quiet, RREHD2 or phase 3 should go ahead. They come first. Before approving the spending, the Board should know what would change, how much difference it should make, how that estimate was calculated, what the program would cost and when the larger changes might arrive. In other words, they establish what is being bought. --- *Colophon: researched and drafted in collaboration with Claude (Anthropic).* --- *Sources: signed minutes of the Sonoma County Aviation Commission meeting of April 16, 2026; FAA records produced in response to FOIA request 2026-04927, including the KSTS Categorical Exclusion Declaration and the "KSTS\_23323 CATEX Form Export" submitted March 23, 2023; Press Democrat reporting of July 6, August 19, August 20 and August 21, 2026\. A companion piece covers the Bohemian Grove routing episode and what it demonstrated.*