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FAA research seeks to understand and minimize the effects of aviation noise on residential communities while maintaining the highest safety standards.

Through NextGen, the FAA has outlined initiatives to achieve its 2020 carbon-neutral growth goal.

The FAA awarded $100 million in CLEEN II contracts to develop technologies that reduce fuel consumption, emissions, and noise.

The FAA and its NextGen program aim to balance environmental protection with sustained aviation growth.

NextGen's overarching environmental performance goal is protection that allows sustained aviation growth. The primary environmental and energy issues that significantly influence the capacity and flexibility of the National Airspace System (NAS) are aircraft noise, air quality, climate, energy, and water quality. These issues are being addressed through a range of environmental laws and regulations and by governmental and industry initiatives.

Major strides to lessen aviation's environmental effects have been made over the past several decades. However, aircraft noise continues to be the public's primary objection to near-term aviation growth. Aircraft exhaust emissions contribute to air-quality-related health effects, as do emissions from all combustion processes, which cause heightened concerns locally and globally. The potential effects of aircraft emissions on the planet's climate may pose the most serious long-term environmental consequences facing aviation. Noise and emissions will be the principal environmental constraints on NAS capacity and flexibility unless they are effectively managed and mitigated.

Operational and infrastructure improvements made through NextGen require environmental review in accordance with the National Environmental Policy Act (NEPA). FAA Order 1050.1F describes procedures for the FAA to implement the act in accordance with federal laws and regulations issued by the White House Council on Environmental Quality, and it facilitates timely, efficient, and effective environmental reviews of FAA actions, including NextGen improvements.

The principles that guide the FAA in addressing environmental and energy issues are:

  • Limiting future environmental impacts of aviation to levels that protect public health and welfare
  • Ensuring energy availability and sustainability

In adhering to these principles, the FAA is pursuing these goals:

  • Air quality: Reduce significant air quality health and welfare impacts attributable to aviation, notwithstanding aviation growth
  • Water quality: Limit adverse aviation discharges into American waters and reduce aviation's significant effects on water quality
  • Climate: Limit the impact of aircraft carbon dioxide emissions on the global climate by achieving carbon-neutral growth by 2020, and reducing the climate impact from all aviation emissions by 2050
  • Energy: Improve NAS energy efficiency, and develop and deploy alternative jet fuels for commercial aviation
  • Noise: Reduce the number of people exposed to significant noise around U.S. airports, notwithstanding aviation growth, and provide additional measures to protect public health and welfare, and national resources

plane flying over wheat field

NextGen is a worldwide leader in reducing aviation's impact on the environment through measures that lower noise, fuel consumption, and engine exhaust emissions.

The FAA Office of Environment and Energy is pursuing a five-pillar approach to meet its environmental goals:

  • Advance sustainable alternative jet fuels
  • Accelerate maturation of new aircraft technologies
  • Explore air traffic management modernization and operational improvements
  • Improve scientific knowledge and enhance integrated environmental modeling capability
  • Develop policies, environmental standards, and market-based measures

Environment and Energy Today

Internationally, NextGen is one of the most substantial programs to save fuel and reduce aviation's impact on the environment. NextGen also has the potential to reduce community noise. The modernization effort increases the efficiency of aircraft operations in the air and at airports. Reduced fuel consumption lowers carbon dioxide and other aircraft exhaust emissions that adversely affect air quality. Operational changes like optimized profile descents can decrease the amount of noise generated by an aircraft. NextGen capabilities like Performance Based Navigation also support reductions in fuel consumption, emissions, and noise. NextGen, the Office of Environment and Energy, and the rest of the FAA work together to achieve environmental protections that enable sustained aviation growth.


The FAA is working to address the public concerns regarding aviation noise, including those related to the changes associated with NextGen. The FAA has the ability to affect aircraft noise through regulation of source emissions, flight operational procedures, and by managing the air traffic control system. The FAA aims to minimize the impact of noise on residential areas consistent with the highest safety standards. Additionally, the FAA performs research to understand the impacts of aviation noise on communities.

The FAA's noise goal is to reduce the number of people exposed to significant aircraft noise around airports to less than 300,000 by 2018. In this context, significant noise is defined as a day-night average sound level of 65 decibels. This graph illustrates the downward trend in noise despite air traffic growth:

The Historical Record: Order of Magnitude Noise Exposer Reduction Despite Traffic Growth.

The number of passengers soared while the number of people exposed to significant aviation noise plummeted over the past 40 years.

The FAA is adopting a new noise standard for certain newly certificated subsonic jet airplanes and subsonic transport category large airplanes. The noise standard, known as Stage 5, applies to any person submitting an application for a new airplane design with a maximum certificated takeoff weight of 121,254 pounds or more on or after December 31, 2017; or with a maximum certificated takeoff weight of less than 121,254 pounds on or after December 31, 2020. This change will set a lower noise limit for newly certificated airplanes and harmonize the noise certification standards for those airplanes certificated in the United States with those certificated under international standards.

A survey regarding the relationship between aircraft noise exposure and its effects on communities around airports was completed in fall 2016. It was the largest survey of its kind. Ten thousand households in 20 communities were surveyed to understand their annoyance with aircraft noise.

In addition, the FAA is conducting research in other impact areas, such as sleep disturbance, cardiovascular health, and children's learning. The FAA recently completed a sleep disturbance field study around a single airport. The research focused on exploring the methodology for a national sleep study that is currently being planned. The FAA is also examining the potential noise impacts of new entrants such as unmanned aircraft systems (UAS), commercial space vehicles, and civil supersonic aircraft.

Improving Understanding

To help industry understand the impacts of noise and emissions, as well as develop solutions to mitigate those impacts, the FAA, NASA, the Department of Defense, Transport Canada, and the Environmental Protection Agency (EPA) fund the Aviation Sustainability Center (ASCENT). ASCENT is the FAA Center of Excellence for Alternative Jet Fuels and Environment. It is a coalition of 16 leading U.S. research universities and more than 60 private-sector stakeholders committed to reducing aviation's adverse environmental impact. Research conducted through ASCENT contributes to developing international aviation emission and noise standards.

Carbon Dioxide Standard

Emissions from aviation operations have an impact on human health and contribute to global climate change. Through NextGen, the FAA has outlined plans and initiatives for improvements in technology, operations, policies, and standards to achieve its 2020 goal of carbon-neutral growth.

In February 2016, the United States and 22 countries reached an agreement on a first-ever global aircraft carbon dioxide standard. The aim is to encourage more fuel-efficient technologies to be integrated into aircraft designs. When fully implemented, the more-efficient requirements are expected to reduce carbon emissions by more than 650 million metric tons between 2020–2040, which is the equivalent of taking 140 million cars off the road.

The rules were agreed upon through the International Civil Aviation Organization (ICAO), the United Nations' aviation technical body, which provides a global forum for 191 member states to adopt and implement international aviation standards.

The new global carbon standards will apply to aircraft manufacturers once they are formally adopted by the ICAO Council. Going forward, ICAO will complete a review of new and emerging aircraft technologies and consider further adjustments to the standards by 2019.

Non-Volatile Particulate Matter Emissions Standard

Another new environmental measure was recommended by the ICAO Committee on Aviation Environmental Protection in February 2016. The committee approved the way non-volatile particulate matter (NVPM) emissions are measured. It applies to nanometer-sized particles that suspend in the atmosphere and become a nucleus for creating clouds or contrails. Medical evidence indicates that fine particles may impact human health. Additionally, suspended particles reflect solar radiation and may influence climate change.

The measurement standard replaces the 1970s-era "smoke number" — a figure that describes the visibility of emissions — with a much more accurate measure of emissions particles. While the smoke number has been effective in reducing visible emissions from aircraft engines, it is inaccurate for modern, low-emissions engines. The NVPM standard is more accurate than the smoke number measurement and reduces manufacturers' cost of compliance.

CLEEN Technologies

Historically, new technologies offered the greatest success in reducing aviation's environmental impact. New engine and airframe technologies continue to play key roles in achieving environment and energy goals. The FAA's Continuous Lower Energy, Emissions, and Noise (CLEEN) program is a public-private partnership under NextGen that seeks to accelerate development and commercial deployment of more-efficient technologies and sustainable alternative fuels. The aircraft technologies focus on reducing fuel burn, emissions, and aircraft noise.

In 2010, the FAA awarded five-year agreements to Boeing, General Electric (GE), Honeywell, Pratt & Whitney, and Rolls-Royce to develop CLEEN aircraft technologies and advance alternative jet fuels. The companies matched or exceeded FAA funds in this cost-sharing program. Over the five-year period, the FAA invested $125 million. The participating companies funding brought the program's total investment to more than $250 million.

Products developed under the CLEEN banner include many jet engine technologies, wing and aerodynamic technologies, automation and flight management systems, as well as fuels and materials.

Diagram of the inner workings of a jet engine

New jet engine technologies developed through CLEEN help reduce aviation's impact on the environment.

One program highlight is the maturation of GE's Twin Annular Pre-mixing Swirler (TAPS) II Combustor. A combustor is a chamber in a jet engine where fuel mixes with an oxidizer to form the explosive energy needed to propel the aircraft. Results show the combustor reduced takeoff and landing nitrogen oxide emissions by more than 60 percent compared to the ICAO nitrogen oxide standard adopted in 2004. This combustor is being used in CFM International's Leading Edge Aviation Propulsion high-bypass turbofan engine, also known as the LEAP, which entered into service in July 2016. GE received more than 8,000 orders for this component to be used in engines for Airbus, Boeing, and the Commercial Aircraft Corporation of China.

Alternative Jet Fuels

Alternative jet fuels are a key element of the FAA's strategy to address aviation's environmental and energy challenges. They can replace petroleum jet fuels without the need to modify engines and aircraft. These fuels will provide economic development in regions where fuel feedstocks are produced, while reducing emissions and enabling the use of waste products. They also expand jet fuel supplies, thereby improving price stability and enhancing supply security.

The FAA's efforts were instrumental in enabling United Airlines to use alternative jet fuels in its day-to-day operations at Los Angeles in 2016.

The FAA has taken a comprehensive approach to overcome barriers in developing and deploying alternative jet fuels that are drop-in replacements to fuels derived from petroleum. Ongoing research and development has focused resources on testing to ensure the fuels are safe to use; analyzed processes to understand benefits, production potential, and challenges to establishing supply; and coordinated with industry, federal agencies, and international stakeholders. These efforts are largely being done through the CLEEN program and ASCENT. The FAA facilitates exchange among the alternative jet fuel stakeholder community through the Commercial Aviation Alternative Fuels Initiative (CAAFI). The FAA helped found the coalition and celebrated 10 years working toward the deployment of alternative fuels in May 2016.

Environment and Energy Ahead


Since the late 1970s, the number of people exposed to significant aircraft noise has decreased by more than 95 percent while operations have more than doubled. Even with this decrease, community concern regarding aircraft noise is increasing. Additional research is needed to understand the impact of aviation noise so that we can develop more effective means of noise control.

plane flying over a playground

Aviation noise is a principal environmental constraint on NAS capacity and flexibility unless it is effectively managed and mitigated.

The FAA will soon have research data that shows the relationship between aircraft noise exposure and its effects on communities around airports. The results of the survey of residents around 20 airports will be completed in 2017. The FAA will use these results and other research that's underway to re-evaluate the criteria it uses to define significance under NEPA and federal land use guidelines.

Additionally, the FAA is measuring noise of different UAS to help determine an appropriate certification plan. The FAA is also developing with ICAO appropriate standards for civil supersonic aircraft. Research regarding the appropriate certification schemes for UAS and civil supersonic aircraft will continue, and the FAA will also continue to research the appropriate way to quantify the impacts of commercial space actions.


Aviation is responsible for less than 2 percent of the world's annual carbon dioxide emissions, but the number of air passengers is projected to double by 2030. This means more and possibly larger aircraft will be required to transport those passengers. Operations of aircraft weighing more than 60 tons, which include most commercial jets, account for more than 90 percent of international aviation emissions. The new carbon dioxide standard applies the most stringent requirements on those aircraft, but the standard also recognizes that those aircraft have access to the broadest range of emission reduction technologies. The next generation of aircraft must be capable of responsibly sustaining emissions reductions.

The completion of the international aircraft carbon dioxide emissions certification standard signals the ICAO member states to begin incorporating the standard within their legislative frameworks. The FAA's new certification regulation will follow the EPA's rulemaking process that adopts the new ICAO standard. Under this schedule, rulemaking on the U.S. aircraft carbon dioxide certification standard is expected to be complete in 2019. The rules will apply to new aircraft designs by 2020. In 2023, the new standards will apply to in-production aircraft that weigh less than 60 tons and have a maximum passenger capacity of 19. Remaining non-compliant planes still in production would be modified to meet the standards or phased out by 2028.

Now that the ICAO has adopted a standard on how to measure NVPM, the next step is to develop a stringency standard for aircraft engine certification. The stringency standard for modern jet engines will be based on health and climate impacts of NVPM rather than the visibility of exhaust.


The Aviation Environmental Design Tool (AEDT) is the government's officially mandated tool for assessing the environmental impact of federal actions at airports as well as on air traffic, airspace, and aviation procedures. This FAA software quantifies environmental impacts of aviation, from a single flight up to full-scale global assessments. AEDT dynamically models a flight, taking into account the aircraft weight and performance characteristics and weather conditions, and calculates the resulting noise, air quality, greenhouse gas emissions, and fuel burn. It also quantifies the environmental impact of changes in a flight's trajectory or selection of equipment.

The FAA's Office of Environment and Energy continuously improves AEDT to increase the understanding of aviation impacts on our environment and to keep it at the forefront of aviation environmental modeling methods.


CLEEN II, a five-year public-private partnership, builds upon the original program's success. It is a key part of the FAA's NextGen efforts to make aviation more environmentally friendly. The FAA awarded $100 million in contracts to companies in 2015 to begin the second phase of the CLEEN program. The companies will develop and demonstrate aviation technologies that reduce fuel consumption, emissions, and noise.

a view of contrails in the sky over the ocean

The FAA's CLEEN II program accelerates development of technologies that reduce exhaust emissions that may impact human health and influence climate change.

The companies selected to be a part of CLEEN II are Aurora Flight Sciences, Boeing, GE, Delta TechOps/MD Coating Technologies/America's Phenix, Honeywell Aerospace, Pratt & Whitney, Rolls-Royce, and Rohr Inc./UTC Aerospace Systems.

With the companies matching or exceeding the FAA's investment, at least $200 million will be allocated to develop a variety of airframe and engine technologies. CLEEN II will nurture the technologies through crucial phases in their maturation aimed at bringing their products to market.

The goals of CLEEN II are:

  • Lowering cumulative noise levels by 32 decibels relative to the FAA Stage 4 noise standard for jets and large turboprop aircraft
  • Reducing fuel burn by 40 percent relative to the most efficient aircraft in service in 2000
  • Cutting nitrogen oxide emissions during takeoff and landing by 70 percent over the 2011 ICAO standard without increasing other emissions
  • Expediting the commercialization of drop-in alternative jet fuels by supporting the approval process

The FAA anticipates that CLEEN II technologies will be introduced into commercial aircraft by 2026.

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