Sukhoi has defended the technical record of its Superjet 100s after two recent incidents involving landing-gear retraction problems on Aeroflot aircraft.
The airframer insists that design "deficiencies" emerge during the first two years of commercial operations on any aircraft type.
Russia's transport ministry has highlighted two incidents this year during which Aeroflot Superjets experience landing-gear retraction issues.
The first involved aircraft 95017 departing Moscow Sheremetyevo on 18 January while the second, four days later, centred on 95019 on take-off from Kharkov.
Crews received "gear fault" and "door not closed" messages. The ministry has asked for checks on the landing-gear and for results to be sent to the federal aviation regulator.
Sukhoi's civil aircraft division says the incidents are "isolated" and adds: "Aircraft at the plant are improved during the production process."
It says commercial operations with the twinjet type, which is in service with three carriers, have turned up problems with erroneous leakage-detection signals as well as slat extension.
Slat-extension incidents on two other Aeroflot Superjets - numbers 95008 and 95010 - arose last year, prompting an airworthiness directive in June. Aeroflot has 10 Superjets.
Both matters have been "isolated", the airframer says, with service bulletins developed, and the in-service fleet is being modified accordingly.
The landing-gear problem is not systemic, adds Sukhoi, and is "being solved" in co-operation with undercarriage specialist Messier-Bugatti-Dowty.
"Gear-up faults do not qualify as in-flight emergencies," it says. "All other aircraft have been checked and no landing-gear problems were detected."