Why Boeing added serrated engine edges to cut jet noise

Noise regulations have become stricter over time. Starting in the 1970s with ICAO's Stage 1 standards, authorities have continued to tighten limits on aircraft noise. The most recent Stage 5 standards require aircraft to be significantly quieter than previous generations. Airlines operating louder planes may face higher airport fees or restrictions at certain airports.

While chevrons are effective at reducing noise emissions, they come with a drawback: a slight loss of engine thrust—about 0.5%. For airlines working within tight profit margins, even this small decrease can impact operational costs.

Despite this penalty, Boeing chose to use chevrons not only on the Dreamliner but also on other models like the 747-8 and 737 MAX. However, Boeing decided not to include chevrons on its newest model, the upcoming Boeing 777X. Instead, this aircraft will use alternative technologies such as honeycomb acoustic lining and a new nozzle design to achieve similar reductions in noise without sacrificing thrust.

The UK Civil Aviation Authority found that during its first months of service at London Heathrow Airport, the Dreamliner was at least five decibels quieter than comparable models like the Boeing 767 and Airbus A330-200. According to Boeing, chevrons can reduce noise by up to fifteen decibels while allowing airlines to comply with regulatory requirements.

The development of chevron technology began before Boeing adopted it; NASA conducted research in the 1990s that identified chevrons as an effective way to lower perceived engine noise from jets on airport grounds. Other manufacturers such as Embraer have also used similar designs based on these findings.

As of August 2025, more than eighty airlines operate Dreamliners worldwide—with All Nippon Airways (ANA), United Airlines, and American Airlines among those with large fleets—and over half of all orders are for the mid-sized 787-9 variant. Despite high development costs estimated above $30 billion and uncertainty about when or if it will break even financially for Boeing,the program has surpassed two thousand orders.

For future widebody models like the Boeing 777X due next year,Boeing is relying on new GE9X engines equipped with advanced nozzle designs and acoustic treatments instead of chevrons to meet modern noise requirements while improving efficiency.