United Airlines has formally launched the new split-scimitar winglet for the Boeing 737 by ordering 135 sets for its 737-900ER fleet.
It had previously indicated in January that it would take the newly-designed winglet, developed by Aviation Partners Boeing.
Aviation Partners Boeing disclosed the formal deal for the modification as the Paris air show opened.
United Ailrines will retrofit the current blended winglets on the -900ER with the split-scimitar tips. The change involves replacing an aluminum winglet tip cap with a swept scimitar cap, and adding a lower ventral strake.
Vice-president of fleet Ron Baur says the scimitar winglet will offer a "natural hedge against rising fuel prices" by reducing consumption.
The winglet will save enough fuel, claims the manufacturer, to allow the -900ER to increase its payload by 1.5t or extend its range by 60nm (110km).
Aviation Partners Boeing is aiming to secure US Federal Aviation Administration supplemental type certification for the 737-800 in October, and obtain similar European approval within the following two months.
It says that certification flight testing of the winglets on the -900ER will then follow "closely behind", starting in November, with FAA certification intended in late February 2014.
Six other 737 variants are potentially in line for the modification, including both structurally-provisioned and non-provisioned 737-700 and -800 airframes.
Aviation Partners Boeing is also hoping to certificate an enhancement in low-speed performance to improve operation from hot and high runways.