Sukhoi's civil aircraft division is preparing for the first flight of the serial-production Superjet 100 this summer, as it starts winding down its flight-test programme.
The first of the four flying prototype twin-jets has completed its work, after 280 flights, and the airframer aims to finish the test phase with three aircraft, plus the static and fatigue airframes.
"We do not plan to allocate one more aircraft for [flight] testing," says a spokeswoman for Sukhoi.
The manufacturer has been battling a bottleneck for the PowerJet SaM146 engine, and admitted earlier this year that it was being forced to share engines between the prototypes and initial production aircraft.
PowerJet, which developed eight flight-test engines for the programme, is expecting to start sending production engines to Sukhoi this month.
Together the prototype jets had accumulated 1,800 flight hours in 705 flights by 2 July. Recently-completed operational tests have included wet-runway runs and cold-soak, while the SaM146 has obtained European certification.
The static testing is largely complete, says the spokeswoman, with items such as the strength of passenger cabin installations still outstanding. Tests on the nose landing-gear have ended successfully, while that for the main landing-gear is nearing conclusion.
Range verification has been conducted by operating the aircraft on routes from Moscow to St Petersburg, Murmansk and Kazan, while aircraft 95005 has undertaken restricted-visibility certification flights.
Fuel system tests have been "successfully completed", says the spokeswoman, while the avionics capability - including Category I and II landings - is still being assessed.
"Oxygen and fire-protection systems testing is on the way, as well as autopilot, navigation system and autothrottle," she adds.
First flight of the serial-production aircraft is "expected in summer", she says, while Russian certification is to be achieved by the end of the year, with deliveries "to start right after, simultaneously to Aeroflot and Armavia".