A subsidiary of Russian state conglomerate Rostec has filed a U.S. lawsuit to cancel its order for 35 Boeing (BA - Get Report) 737 MAX airplanes, another sign that Boeing's customers are losing patience with ongoing delays in remedying the troubled jet.

According to the Financial Times, Avia Capital Services, a subsidiary of Rostec, gave Boeing a cash deposit of $35 million to secure the order of 35 737 MAX jets.

The complaint, which was filed in Cook County Circuit Court in Chicago on Monday, claims that Boeing "intentionally" failed to disclose information about the airworthiness of the MAX to its customers, including Avia, in order to induce them to buy the aircraft, the Financial Times said.

However, an Avia spokesperson told Reuters on Tuesday that it is ready for an out-of-court settlement.

Boeing faces first lawsuit from 737 Max customer https://t.co/ySWycYzgqf

— Financial Times (@FT) August 26, 2019

Steven Marks of Miami aviation-focused law firm Podhurst Orseck is representing Avia. He also is representing 30 families of victims of both the Lion Air crash in October 2018 and the Ethiopian Airlines tragedy this past March which together killed 346 people.

Avia is claiming that two deadly crashes were due to the "negligent actions and decisions of Boeing" not just in designing a plane that was "defective" but also in "withholding critical information" from the U.S. aviation safety regulator during certification, according to the suit.

Meantime, the grounded MAX could be certified and back in service as early as October, according to recent reports.

Shares of Boeing were down just over 1% at $355.71 in early trading on Tuesday.

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