Lufthansa Technik and BASF wrapped a 777 in shark skin and cut its fuel burn ~1%

Airlines cut fuel burn with lighter seats, better routing and wingtip devices, leaving the fuselage as smooth as paint could make it. Lufthansa Technik and BASF went the other way. They developed AeroSHARK, a film carrying microscopic ribs modelled on shark skin, stuck to the fuselage to cut frictional resistance and, with it, fuel and CO2 emissions by around one percent.

Getting a surface film onto an airliner was a certification problem, not a materials one. The first aircraft, Swiss's Boeing 777-300ER HB-JNH, went into modification at the end of August 2022 and flew the certification programme with EASA on 8 and 9 September, where proof was required that the change had no negative impact on safety or handling. From October it flew daily services under a temporary Permit-to-Fly from the Swiss Federal Office of Civil Aviation, valid for that one aircraft only, while weeks of data evaluation and flow simulations went through EASA's review.

In December 2022 EASA granted Lufthansa Technik a Supplemental Type Certificate for series conversion of two Boeing 777 variants, the 777-300ER and the 777F. Launch customers Lufthansa Cargo and Swiss had retrofits scheduled in Frankfurt and Zurich for January, and committed to fitting all twelve 777-300ERs and eleven 777Fs — the first airlines to optimise a whole sub-fleet with riblet film. Per aircraft the saving is around 400 tonnes of kerosene and more than 1,200 tonnes of CO2 a year on a Swiss 777-300ER, and 370 tonnes of fuel and 1,170 tonnes of CO2 on a Lufthansa Cargo 777F.

The mechanism is measured rather than assumed. A 2018 paper in Friction 3D-printed ABS surfaces carrying shark-skin-like scales at a series of orientations and tested them in a rheometer. The surface with scales at 90 degrees to the flow gave the lowest viscous drag, with a viscosity reduction of up to 9%. Mapping the flow with fluorescent diamond particles showed the reduction came from a lower velocity gradient near the surface — the same near-wall effect a riblet film exploits on a fuselage.

Make the skin deliberately ribbed, not smoother

Winglets and weight savings act on induced drag and mass; riblets act on skin friction, which neither of those measures touches.

One percent sounds trivial until it is multiplied by a sub-fleet: more than 25,000 tonnes of CO2 a year across the Lufthansa Group's Boeing 777s.

The retrofit was slotted into maintenance work in Frankfurt and Zurich, so the film went on while the aircraft was already on the ground.

Certification, not the material, was the bottleneck — a single-aircraft permit-to-fly let it earn operating data while EASA finished its review.

A one-percent gain nobody thinks is worth a type certificate becomes 25,000 tonnes of CO2 a year across a sub-fleet — if it can go on during a maintenance visit already booked.

With the STC in hand, Swiss and Lufthansa Cargo began fitting their entire 777 fleets, twelve 777-300ERs and eleven 777Fs, worth more than 25,000 tonnes of CO2 a year to the Lufthansa Group. Lufthansa Technik and BASF said they would develop AeroSHARK further for other aircraft types and for larger areas of the airframe; in initial model calculations the technology at its maximum expansion stage could avoid CO2 emissions of up to around three percent. The route became the template: prove it on one aircraft under a temporary permit, then convert fleets under a type certificate.