United Airlines on Wednesday became the first major U.S. airline to debut the most recent innovation in a series of wing tweaks that are imperceptible to most people. The “Split Scimitar” winglet is thin, curved, and more aerodynamic than its predecessor. It will replace the previous generation of “Blended” winglets on United’s Boeing Next Generation 737 fleet.

Winglets are ten-foot extensions at the tip of planes’ wings that exist to direct air more efficiently around the craft, reducing in-flight turbulence and drag. They only became popular with airlines in the early 2000s as fuel costs rose and carriers looked to cost-saving solutions.

United Airlines’ upgrade will cut the fleet’s energy use by two percent, which combined with other recent winglet upgrades will save the company $200 million per year, United said in a press release.

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Split Scimitar winglet sketch from aviationpartnersboeing.com

Photo Credit: The Split Scimitar Winglet on a United Boeing 737 United Airlines