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Is it possible to fly "green" and have a little legroom?

Published Wed, 2016.03.16 | By

Irene Kwan

In airline economy class, the tradeoff for lower fares includes less seat space—sometimes a lot less. Nobody likes it. But does that ever-shrinking legroom also mean so much higher fuel efficiency that we should just stop complaining?

At first glance, you might think so. Our recent study ranking the top 20 airlines on fuel efficiency for transatlantic flights found a 51% gap between the least and most efficient airlines in 2014. Seating configuration, measured in terms of seating density or the available seats per square meter floor area, was the most important factor in that gap, accounting for about 46% of the variation in airline fuel efficiency.

We modeled the fuel burn of a typical flight on Airbus A330-300 aircraft across the Atlantic—“typical” meaning 6,700 kilometers (~4,160 miles), 83% passenger load factor (across all seat classes, although it can vary significantly by seat class), and carrying 4,500 kilograms belly-freight payload—using the Piano-5 model. Figure 1 shows the overall fuel efficiency in passenger kilometers per liter of fuel (pax-km/L) along with the aircraft seat count for a specific aircraft for each of 12 airlines.

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Figure 1. A330-300 overall fuel efficiency vs. seat count on a typical transatlantic flight. (Source: www.seatguru.com; author's calculations)

Not surprisingly, airlines with overall higher seating densities are more fuel-efficient than those with lower seating densities. The amount of economy seating varies significantly from one aircraft (or airline) to the next (Figure 2), and so does the amount of floor space available for the different class cabins, which we estimated from airline seat maps using rectangular sections (Figure 3). Overall, the share of floor space for economy seating is less for every airline than the share of seats.

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Figure 2. A330-300 share of seats by seat class. (Source: www.seatguru.com)

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Figure 3. A330-300 share of seats by floor area. (Source: www.seatguru.com; author's calculations)

But the reality is not quite so straightforward. To get at the question whether it's possible for flying to be both greener and at least a little bit roomier, we first need to define “roomy.” Groups such as the National Association of Airline Passengers and FlyersRights.org have petitioned the FAA to mandate minimum seat pitch (an approximation for legroom: the distance from a point on one seat to the same point on the seat in front) and width for commercial airlines; the NAPA proposed a 19” minimum seat width and 36” minimum seat pitch. Airbus, in 2013, proposed a minimum seat width standard of 18 inches for long-haul economy air travel, which it claims could improve passenger sleep quality by 53% compared to the 17-inch standard from the 1950s that prevails now. Some argue that setting minimum seat pitch at the pre-deregulation average of 34 inches “would help avoid future seat-rage incidents”.

Replacing tight economy seating with seats meeting such minimums would be equivalent to the increasingly common “Premium Economy” or “Economy Plus” or “Comfort+” classes. The largest U.S. airline, American Airlines, recently introduced premium economy on its long-haul aircraft, joining a growing list of global carriers that already includes Lufthansa and Singapore Airlines.

If minimum seat standards were met by replacing economy and “premium economy” with 34-inch pitch and 18-inch width seats, fuel efficiency could be maintained for the most part and even improved. Take, for example, the Boeing 787-8 aircraft flown by Norwegian Airlines—presently the most fuel-efficient airline in the transatlantic market. If the 259 standard seats and 32 premium economy seats on a Norwegian aircraft were transformed into a one-class cabin with 34-inch pitch and 18-inch width seats, it could achieve at least a 275-seat configuration, making the simple assumption that the total seating area is preserved. (A 3-3-3 economy seating configuration like that of THAI Airways’ 787-8, which has 18-inch width economy seats, could yield an even higher number of seats). This is only about 5% fewer seats than the current configuration, and Norwegian would still lead in efficiency. Norwegian had the highest fuel efficiency because of its relatively high seating density and efficient aircraft. In comparison, Icelandair uses much older, less efficient 183-seat Boeing 757-200 aircraft. Although it had the highest seating density of about 1.35 seats per square meter—34% higher than the average—among the transatlantic carriers, Icelandair ranked much lower in fuel efficiency overall, burning about 26% more fuel per passenger kilometer than Norwegian.

Other airlines with many business seats and fewer economy seats, such as British Airways, could potentially increase their total seat counts via a minimum seat standard cabin and thus gain in fuel efficiency per flight (assuming load factors remained the same, although they would likely change with seating class). For example, British Airways’ prevalent 747-400 aircraft, which has a 345-seat configuration (243 economy, 36 premium economy, 52 business, and 14 first), could improve fuel efficiency by at least 25% without the cost of comfort to its economy passengers with a one-class cabin of seats meeting minimum standards of 18-inch width and 34-inch pitch, using a 4-3-4 seating configuration like that of Korean Air, and achieving at least 434 seats on the aircraft like Air France, which has one of the densest 747-400 aircraft.

So what's the upshot? More efficient aircraft combined with a one-class cabin having minimum seat standards could give a lot more people a lot more comfortable flights without giving up much, if anything, in fuel efficiency. And that—to repurpose an old airline advertising slogan—would make for much friendlier skies.