When you burn as much fuel as an airline does, a single-digit fuel efficiency tweak adds up to massive savings. Take the drag-reducing Aeroshark film Swiss Airlines has stuck all over its 12 Boeing 777s – it delivers a 1% efficiency gain, and as a result, over just 12 aircraft, Swiss expects to use 4,800 tonnes less jet fuel every year, saving nearly half a million dollars per year, per plane at today’s prices. That’d be closer to half a billion a year for an operator like American Airlines, closing in on 1,000 planes in its fleet, from a 1% efficiency gain.

So you can see how an airliner 30% more efficient than today’s best single-aisle machines could be a bit of a big deal. We first ran across Boeing’s “truss-braced wing” design concept back in 2010, as a part of the “Subsonic Ultra Green Aircraft Research” (SUGAR) Volt concept it designed as part of a NASA research program.

The idea takes advantage of the higher lift and lower drag you get with longer, slimmer, high aspect ratio wings – the sort you might find on an unpowered glider. A concept Boeing was testing in 2016, for example, had wings some 50% wider than comparable standard aircraft.

Structurally, that kind of thing simply doesn’t work without reinforcement. So Boeing’s design hangs the wings from the top of the fuselage, and braces them with long trusses coming up from the belly of the plane. These too are carefully shaped airfoils, adding extra lift as well as strength and stability.

As a subsonic concept cruising at around Mach 0.70 to 0.75 (519 to 556 mph, 835 to 895 km/h), Boeing estimated these braced-wing airliners could burn 50% less fuel than a regular plane. In 2019, the concept was redesigned to cruise at the edge of transonic speed, around Mach 0.8 (593 mph, 955 km/h), and whether because of the added speed or simply from a better understanding of the aerodynamics, Boeing has walked the efficiency claims back.

“When combined with expected advancements in propulsion systems, materials and systems architecture,” reads a Boeing press release, “a single-aisle airplane with a TTBW configuration could reduce fuel consumption and emissions up to 30% relative to today’s mos