Airplanes are kind of a big deal. They transport about 35 percent of all trade happening on Earth, and about 3 billion people fly every year. All that transit takes a lot of energy: A third of airline operating costs are spent on fuel, and the exhaust of all that gas accounts for an estimated 2–3 percent of global carbon-dioxide emissions.
The depressing thing, as a new National Bureau of Economics Research working paper lead-authored by London School of Economics researcher Greer Gosnell points out, is that oftentimes pilots fail to take advantage of the many straightforward ways they can reduce their airliners’ environmental impact. These aren’t complicated tricks: It’s cutting an engine while taxiing, or adjusting altitude or route to optimize fuel efficiency. Pilots have lots of autonomy about flight trajectories and the like, but like any other humans, they have blind spots and can slip into inefficient patterns.
For the paper, the researchers asked what would happen if they nudged Virgin Atlantic Airways pilots to do a bit better on this front. Tracking 40,000 flights flown by 335 captains, the researchers first sent all Virgin captains a letter explaining that the company was participating in a field experiment in sustainable behaviors over eight months. For the rest of the experiment, the pilots were divided into four groups; “information,” where pilots got a monthly feedback report on their fuel-relevant behaviors; “targets,” where they got that same feedback with added personal goals; “prosocial incentives,” where pilots got both the information and targets, but also the promise of a £10 donation to a chosen charity for each target met in a given month, up to £240 over the course of the trial; and a control group whose members were informed that they were being tracked but for whom it was otherwise business as usual.
The results were both impressive and frustrating. The most surprising thing was the change within the control group: From just being told that they were monitored, these pilots jumped from meeting the “efficient flying threshold” — described as using less fuel by “requesting and executing optimal altitudes and shortcuts from air traffic control, maintaining ideal speeds, optimally adjusting to en route weather updates” — on 31 percent of flights to 47 percent of flights, and their efficient taxiing jumped from 35 percent of the time to 50 percent. The feedback group jumped in efficient flying from 31 percent of the time before the experiment to 50 during the experiment, and the personal-target group didn’t improve much on preflight efficiency (which concerns making right fuel-load estimates) but nearly doubled their attainment of the efficient flying and efficient taxiing metrics before and during the experiment. In somewhat disappointing news, the promise of giving money to charity didn’t do much beyond giving people targets, and the only improved behavior to stick around after the experiment was the efficient taxiing — since, pilots said in interviews, it was the easiest thing to do. (This is a classic example of what environmental economists call “free gains”: with a small adjustment, you can make employees’ behavior way more sustainable.)
Still, despite the mixed results, the overall fuel savings were pretty huge: The authors estimate that their interventions saved between 266,000 and 704,000 kilograms of fuel, equivalent to a $209,000 to $553,000 value and a staggering 838,000 to 2,220,000 kilograms of carbon dioxide being abated. Just imagine if a field experiment like this were extended to the every airline: With enough nudges, you could change an entire industry.