Why does the fuel efficiency of the same airline differ across markets?

Since 2011, the ICCT has been comparing the fuel efficiencies of major airlines in various markets, including U.S. domestic, transatlantic, transpacific, and, most recently, U.S.–Latin America. Three U.S. legacy carriers–American, Delta, and United­–claim a large share of each of these U.S.-international markets and are also the only carriers operating in all three segments. One would expect that the overall fuel efficiency and aircraft fuel burn for each carrier would be reasonably consistent in each market. But are they?

The table below shows the average fuel efficiency by carrier and by market, along with the revenue passenger mile (RPM) weighted average fuel efficiency across the four markets for each carrier. The carriers operated at very similar fuel efficiencies of 32 and 33 passenger-kilometers per liter of fuel (pax-km/L) on a weighted average basis. Meanwhile, the U.S. legacy carriers’ relative performance to other carriers varied by market. In the transpacific market all three legacy carriers operated at fuel efficiencies above market average, but the opposite was true for the U.S.-South America market. Both external market forces and airlines’ fleet strategies can help explain this apparent discrepancy.

Table. Average fuel efficiency (FE) in pax-km/L by carrier and by international market.
Market American Delta United Market total
Avg. FE Billion RPM(%) Avg. FE Billion RPM(%) Avg. FE Billion RPM(%) Avg. FE Billion RPM(%)
Transpacific (’16) 33 13.4 (6%) 32 21.0 (10%) 32 32.8 (16%) 31 210.1 (100%)
Transatlantic (’17) 33 29.3 (8%) 34 41.5 (11%) 31 36.2 (10%) 33 363.2 (100%)
U.S.-SA (’18)* 34 15.1 (29%) 34 5.8 (11%) 33 7.2 (14%) 37 53.0 (100%)
U.S.-MCC (’18)* 30 15.5 (18%) 32 12.8 (15%) 34 13.7 (16%) 32 87.4 (100%)
Weighted Avg. FE  33 33 32 33

*The U.S.-Latin America market was broken into two segments: U.S.-Mexico, Central America, and the Caribbean (U.S.-MCC), and U.S.-South America (U.S.-SA).

The markets analyzed feature different average stage lengths, customer demands, and competitive landscapes. These factors all affect operational strategies and, therefore, fuel efficiency. For example, transpacific flights on average have more premium seats than flights to other regions, resulting in lower average seating density. This, along with the longer stage length, is a major reason why the transpacific market overall demonstrated lower fuel efficiency in terms of passenger kilometers moved per liter of fuel.

Carriers also operate different aircraft for similar routes in the same market, leading to different levels of fuel efficiency. The fuel burn of an airline’s fleet is a major driver of overall fuel efficiency. The figure below shows each airline’s RPM weighted average margin to ICAO’s CO2 standard for in-production aircraft, as well as the average margins of the four markets. Negative values indicate the use of aircraft with lower fuel burn, while positive values indicate a fleet made up of more fuel-intensive aircraft.

The fuel burn margins of American’s fleets were similar in the transatlantic and U.S.-Latin America markets, whereas the carrier’s fleet fuel burn was exceptionally low for its 2016 transpacific flights due to the use of Boeing 787 Dreamliner aircraft. The carrier plans to modernize its fleets in the other international markets with Dreamliners as well. The planned fleet renewal would likely narrow the gap of aircraft fuel burn among these markets. The carrier overall operated fleets with lower (better) fuel burn than the respective market average except in the U.S.-South America market, which is where it claims the largest market share (29%). The heavy use of Airbus 319 aircraft for relatively short flights to Colombia, Brazil, Ecuador, and Guyana was a contributing factor.  

Delta’s fleets were relatively fuel-inefficient in the transpacific and U.S.-MCC markets, hurt by the use of Boeing 747s for the former and older models of the Airbus 320 series for the latter. The carrier flew mostly Boeing 767-300 series aircraft on its transatlantic and U.S.-South America routes, and achieved near industry average fleet fuel burn in both markets. With that being said, Delta could further improve its fuel efficiency through fleet renewal in all four markets, as it plans to modernize its fleets with Airbus 350-900s and 330-900neos.  

United operated fleets with the most consistent fuel efficiencies across markets among the three legacy carriers, exceeding the ICAO standard by 6% in three out of the four international route groups. United’s fleet for U.S.-South America operations was slightly less carbon-intensive, partially thanks to the use of Boeing 767-300ER aircraft, whereas its transpacific and transatlantic flights were often flown by the less efficient Boeing 747s and 777-200ERs. Nevertheless, the planned replacement of 747s with 777-300ERs and 777-200ERs with Airbus 350-900s could dramatically improve the carrier’s fuel efficiencies in the transpacific and transatlantic markets.

As shown, the three legacy carriers applied different fleet strategies across the U.S.-international markets. No one carrier consistently deployed aircraft with lower fuel burn than its peers across the four route groups, though American tended to use aircraft with lower fuel burn in many international markets. We observed the largest deviations of aircraft fuel burn within individual airlines in American’s transpacific fleet, which was exceptionally more fuel-efficient than its fleets in other markets, as well as in Delta’s transpacific and U.S.-South America fleets, which were significantly more fuel-intensive than aircraft used on Delta’s other routes.

Later this year, ICCT will update its transpacific and transatlantic fuel efficiency rankings with 2018-2019 data, allowing more parallel comparisons with the U.S.-Latin America market. With the fleet renewals in recent years, we will also be able to assess the impact of deploying more fuel-efficient aircraft in different international markets. So, stay tuned.