Outfitted with a new wing made completely of locally produced composite materials, Russia’s Irkut MC-21 narrowbody jetliner will begin flight tests later this year, Russian minister for industry and trade Denis Manturov told journalists on Friday. The fitting of domestic composites on the latest MC-21 marks the latest milestone in the Russian aviation industry’s effort to wean itself from reliance on Western products. U.S. sanctions continue to threaten the viability of the program given the original design’s extensive use of Western parts.

Manturov spoke to the media a day after Irkut Corporation—a state-owned structure that controls the plant in Irkutsk that builds the twinjet and Yakovlev design house that designed it—announced it had received the first set of outer wings from the Ulyanovsk-based AeroComposite company. Irkut said a 17.5-meter-long piece arrived by road, using “special equipment with a system of fasteners and sensors to prevent structural damage during transportation.” It further said that it would fit the wing to a deliverable MC-21-300 airframe that, upon completion of testing, would go to “the first customer.” Earlier, the same airframe received a wing center section also made of domestic materials.

“Leading Russian chemists and technologists, including experts and academics from Moscow State University and Rosatom, participate in the development and production of domestic composite,” said Irkut in a statement. “The technology used to produce large-scale wing box panels based on infusion technology was developed by the AeroComposite and patented in Russia.”

According to Yakovlev, the use of advanced composite materials and the infusion technology enabled the design house to develop a wing with an aspect ratio of 11.5—notably higher than respective figures for previous-generation narrowbodies, which typically fall between 8 and 9, and larger commercial jets, at 10 to 10.5. The higher aspect ratio results in a higher lift-to-drag ratio and improved aerodynamic performance.

After Irkut resolves the issue of its reliance on Western composite materials, the MC-21 program office will have to address the aircraft’s engines. Given a choice between the Pratt & Whitney PW1400G and Aviadvigatel PD-14, most airlines selected the first option. Even though the U.S. manufacturer did deliver a number of engines, including four operable prototypes, still tightening U.S. economic sanctions on Moscow threaten their availability. The U.S. State Department has warned many times that it may prohibit any further sales of advanced U.S. equipment to Russia, most notably “turbojet engines.” If that threat materializes, Irkut will not be able to deliver to airlines what they've ordered, hence the need to renegotiate early contracts.

Out of 12 airlines that signed for the MC-21, half reside outside Russia. Locally carriers include Aeroflot (firm order for 50 plus options for 35), Red Wings (16 firm), IrAero (10 firm), Yakutia (5 firm and five options), Nord Wing, Angara, and Alrosa. The Russian flag carrier appears unlikely to take early aircraft, preferring to wait until most teething problems get resolved during initial type operations. Therefore, Irkutsk-based Angara and IrAero, as well as UAC-controlled Red Wings, appear the most likely candidates to receive the first batch of MC-21s with PD-14 engines and a local aviation set. Plans call for delivery of those airplanes beginning in 2023.