Russian state corporation Rostekhnologii is intending to purchase 35 Boeing 737 Max twinjets, through its leasing division Aviakapital-Servis.
The agreement marks the first deal for the re-engined aircraft family in Russia, and comes as the airframer plans increased co-operation with an affiliated titanium supplier.
Rostekhnologii has previously disclosed plans to take up to 85 737s, and 50 of these had been firmed. Aeroflot subsequently agreed to lease 50 737-800s and -900ERs from the corporation.
But Rostekhnologii held back from committing to the remaining 35 aircraft in favour of looking at the 737 Max and Airbus A320neo.
Boeing says the new Max deal is potentially worth over $3 billion but has yet to be finalised. All Max variants will be powered by the CFM International Leap-1B engine.
"Our partner airline carriers will receive the most modern aircraft with improved fuel efficiency, flight characteristics and greater comfort for passengers," says Rostekhnologii chief Sergey Chemezov.
"Russian airlines will gain an advantage on global markets and will be able to increase their activity both within the country and internationally."
In parallel with the deal, Boeing is seeking to deepen co-operation with titanium specialist VSMPO-Avisma, in which Rostekhnologii is a major shareholder.
Boeing says the talks cover titanium procurement as well as technology development, including a possible expansion of its joint venture Ural Boeing Manufacturing to support production rate increases of current 737s.
Chemezov says: "Extending co-operation with Boeing will help us create even better and more competitive solutions for the global aviation industry."