Skip to page content

Fact Sheet – Continuous Lower Energy, Emissions, and Noise (CLEEN) Program

For Immediate Release

March 4, 2020
Contact: Henry J. Price
Phone: 202-267-3883

CLEEN is the FAA’s principal environmental effort to accelerate development of new aircraft and engine technologies and advance alternative jet fuels.  The program is a key element of the NextGen strategy to achieve environmental protection that allows for sustained aviation growth.  The FAA launched the initial CLEEN I in 2010.  Over the five-year course of the program several technologies have been tested and are in use today.  Based on that success, the FAA is currently in a second phase, CLEEN II, which runs from 2015 through 2020.

The FAA works with selected industry partners under CLEEN through cost-sharing where companies in the program match or exceed funding provided by the FAA.  Specifically, these companies are developing technologies that will reduce noise, emissions, fuel burn and enable the aviation industry to expedite integration of these technologies into current and future aircraft.

The CLEEN I companies are:

  • The Boeing Co.
  • General Electric (GE) Aviation
  • Honeywell Aerospace
  • Pratt & Whitney (P&W)
  • Rolls-Royce, North America Inc.

The CLEEN I companies matched or exceeded the federal funding of $125 million, bringing the program’s total investment to more than $250 million.

The CLEEN II companies are:

  • Aurora Flight Sciences
  • Boeing
  • Delta TechOps/MDS Coating Technologies Corp./America’s Phenix Inc.
  • GE Aviation
  • Honeywell Aerospace
  • P&W
  • Rohr Inc./United Technologies Corp. (UTC) Aerospace Systems
  • Rolls-Royce, North America

The FAA plans to invest $100 million in CLEEN II, with cost-sharing from industry partners that will match or exceed its federal contribution. The FAA anticipates that developed CLEEN II aircraft technologies will be on a path for introduction into commercial aircraft by 2026.

Through the FAA Partnership for Air Transportation Noise and Emissions Reduction (PARTNER) Center of Excellence, Georgia Tech University conducted an independent assessment of the technologies being matured in the CLEEN Program.  They found that use of the technologies could reduce U.S. fleet-wide fuel burn by 2 percent from 2025 through 2050, representing a cumulative savings of 22 billion gallons of jet fuel.  The CO2 savings are the equivalent of taking 1.7 million cars off the road over the duration of this 25-year period. Georgia Tech is continuing their work to independently assess the CLEEN II technologies through the FAA Aviation Sustainability Center (ASCENT) of Excellence.

The CLEEN Program goals include developing and demonstrating:

  • Certifiable aircraft technology that reduces aircraft fuel burn;
  • Certifiable aircraft technology that reduces Landing and Takeoff (LTO) cycle nitrogen oxide (NOX) emissions below International Civil Aviation Organization (ICAO) Committee on Aviation Environmental Protection (CAEP) standards, and/or reduces absolute NOX production over an aircraft’s mission;
  • Certifiable aircraft technology that reduces noise levels relative to the FAA’s Stage 4 noise standard and/or reduces the noise contour area in absolute terms; and,
  • “Drop-in” alternative jet fuels, including quantification of benefits – drop in alternative fuels will require no modifications to aircraft or fuel supply infrastructure.

The following table represents quantitative aspirational goals for reductions in fuel burn, emissions, and noise for CLEEN I and CLEEN II:

Goal AreaCLEEN I Goals (2010-2015)CLEEN II Goals (2015-2020)
Noise (cumulative below Stage 4)-32 decibels (dB)-32 decibels (dB)
LTO NOX Emissions (Below CAEP/6)-60 percent-75 percent
(-70 percent re: CAEP/8)
Aircraft Fuel Burn-33 percent-40 percent

Some highlights of the CLEEN Program include:

  • In 2011, Honeywell completed testing of Hydro-Processed Esters and Fatty Acids (HEFA) alternative jet fuel which expedited its international approval;
  • In 2015, P&W completed a series of tests in support of ASTM approval of the following alternative jet fuels:  Amyris Direct Sugar to Hydrocarbon (DSHC) Farnesane; Kior Hydrotreated Depolymerized Cellulosic Jet (HDCJ); Applied Research Associates (ARA) Catalytic Hydrothermolysis (CH), and Swedish BioFuel ATJ-SKA;
  • In 2016, GE’s Twin Annular Premixing Swirler (TAPS) II combustor matured under CLEEN I and entered into service as part of CFM International’s TAPS Leading Edge Aviation Propulsion (LEAP) engine, currently onboard Airbus 320neo, Boeing 737 MAX, and COMAC C919 aircraft.  Under CLEEN I, GE engine emissions tests of TAPS II had results that were more than 60 percent below the 2004 ICAO CAEP NOXstandards;
  • Business trade studies are currently being conducted by CLEEN companies for their aircraft technologies to assess opportunities for incorporation of the technologies into aircraft and engine designs; and,
  • The FAA anticipates that more of these technologies could go into service in the next several years.

For a more detailed look at CLEEN I and II go to: and CLEEN I and CLEEN II Projects.