Russian operator Yakutia has signed a tentative agreement to acquire five Irkut MC-21-300s, with two other carriers also reaching preliminary deals for the twinjet type.
Kazakhstan's Bek Air is looking to take 10 aircraft while another five will provisionally go to an unidentified customer.
The agreements – with little further information, and no details on engines or delivery dates – have been disclosed during the MAKS Moscow air show, at which the MC-21 has been displayed.
Irkut's current firm order total for the MC-21 amounts to 175 aircraft and the company has letters of intent or memoranda of understanding covering a further 160.
Siberian carrier Yakutia operates a mixed fleet including Boeing 737s, Sukhoi Superjet 100s, Bombardier Dash 8s and Antonov An-24s.
Bek Air's fleet primarily comprises Fokker 100s.
Irkut has secured funding for MC-21 development through an agreement with state corporation Rostec's financing arm Novikombank.
Novikombank says it has arranged Rb10 billion in finance to support certification and serial production of the MC-21-300, under an agreement signed at MAKS.
"Supporting Russia's advanced industry is Novikombank's top priority," says chairman Elena Georgieva. "This [MC-21] programme gives powerful impetus to development of the entire domestic aircraft industry."
The MC-21 is being certified to Russian standards as well as those of the European Union Aviation Safety Agency.
Irkut president Ravil Khakimov says the manufacturer's "most important" task is to complete certification of the twinjet and start initial deliveries to customers.