Boeing Co. is caught in a bind after the U.S. barred Russian airlines from its skies following the invasion of Ukraine.

The move could affect Boeing’s main wide-body plant in Everett, Washington, near Seattle, where giant Antonov An-124 cargo planes operated by Russia’s Volga-Dnepr Group are used to fly structures from other plants.

The U.S. Transportation Department had authorized Volga-Dnepr to operate at least 27 flights since early 2021, many of them for Boeing, according to regulatory filings. In the latest request, on Feb. 24, the cargo carrier sought permission for six flights by April 4 to haul 11-ton 767 wing boxes from a supplier in Florida.

Volga-Dnepr’s giant Antonov aircraft were the only option “to perform the services in question within the set schedule,” the latest filing said. Timely shipments were vital to avoid substantial delays to Boeing’s production schedule, it said.

“Boeing needs its equipment and components,” said Brian Clancy, managing director of Logistics Capital & Strategy LLC. “The reality of it is that we’re all co-dependent on each other’s planes.”

The now-banned flights by Volga-Dnepr, a long-time Boeing partner and customer, are just one of the ripples through aviation from the sanctions placed on Russia after last week’s invasion. Boeing also has halted much of the engineering work it does in Moscow and restricted employee access in Russia to sensitive data while it seeks U.S. export licenses.

“We work closely with our wide range of supply chain and logistics partners to manage through any potential impacts,” Chicago-based Boeing said of the requested 767 cargo loads. Volga-Dnepr didn’t immediately respond to requests for comment.

Derived from a Soviet-era military cargo jet, the Antonov An-124 has symbolized the rapidly disappearing era of open skies. The world’s largest production air freighter was designed in Ukraine, built in Russia and deployed by Volga-Dnepr globally for missions like providing disaster aid to Puerto Rico.

The only other civil An-124 operator apart from Volga-Dnepr is Antonov Airlines, which is based in Ukraine. The status of that fleet is uncertain and the sole An-225, an even larger six-engine variant, was reported as damaged beyond repair in a battle for Hostomel airport outside Kyiv.