The report, like the prior ICCT studies, uses a frontier model to evaluate and compare fuel efficiency. This approach, ICCT says, enables an equitable comparison of airline fuel efficiency, regardless of business model, through the use of primary fuel burn data and an inclusive metric for transport service—a combination of mobility, measured by revenue passenger miles (RPM), and access, measured by departures (or the flight frequency).

The team then calculated a unitless fuel efficiency score (FES), measuring the transport service (combination of mobility and access) an airline provides per unit of fuel consumed, by normalizing each airline’s inefficiency value by the simple average across all airlines. A higher FES denotes higher fuel efficiency, and an FES of 1.00 represents the average airline.

The Fuel Efficiency Score (FES) is a unitless fuel efficiency metric that indicates the transport service provided by an airline per unit fuel consumed relative to other airlines. A higher FES denotes higher fuel efficiency and an FES of 1.00 (i.e., Hawaiian) represents the average airline in 2014. Source: ICCT. Click to enlarge.

Key findings of the updated study include:

• Alaska, Spirit, Frontier, and Southwest Airlines remained the top four most fuel-efficient airlines on US domestic operations in 2014. On average, Alaska has operated the most efficient US domestic flights for five years running since 2010. America Airlines ranked last for the third year in a row, burning 25% more fuel than Alaska to provide a comparable level of transport service.

• Overall industry fuel efficiency improved by 1.7% from 2013 to 2014. Operational improvements, including a 1% gain in passenger load factor and a 1.6% increase in seating density (upgauging), accounted for most of the observed fuel efficiency gains.

  In 2010, there were 145 seats on an average US domestic flight flown by the mainline carriers. In 2013 this number rose to 149, and reached 150 in 2014. This steady increase in seats available per flight result in increased fuel efficiency but at the cost of reduced passenger comfort and access to flights (fewer airports served and/or longer wait times between flights).

• The US domestic fleet for the 13 airlines was found to be slightly younger in 2014 (average 11.5 years old, weighted by passenger-miles flown) than in 2013, while previous years showed an aging fleet.

• A stronger correlation between fuel efficiency and profitability was observed in 2014 than in 2013, despite a sharp fall in oil prices in the latter half of the year.

Commercial aircraft accounted for 11% of greenhouse gas (GHG) emissions from the US transportation sector in 2013. The Federal Aviation Administration (FAA) estimates that under a business as usual scenario, GHG emissions from US aviation will increase by more than 100% by 2050 compared with 2005 levels, and even faster growth is expected globally. In July, the US Environmental Protection Agency (EPA) proposed to regulate aviation greenhouse gas (GHG) emissions from aircraft under the Clean Air Act (CAA).

Resources

• Guozhen Li, Irene Kwan, and Daniel Rutherford (2015) “US Domestic Airline Fuel Efficiency Ranking, 2014”