Test personnel from the European air safety regulator have completed a second series of certification flights with the Irkut MC-21.
The European Union Aviation Safety Agency had undertaken an initial set of flights with the twinjet in January this year, following a training and authorisation session the previous September.
Irkut states that a second round was carried out in June, in co-operation with federal air transport regulator Rosaviatsia.
The aircraft has been flown in various modes up to altitudes of 12,000m (39,400ft).
Irkut adds that the EASA testing involved take-off at high and low weights, with different balance configurations forward and aft.
"Operation of the integrated aircraft control system in the normal mode has been verified," it says, and pilots have examined the MC-21's performance at minimum take-off and landing speeds, and during engine-out conditions.
"Completion of the second session of certification flights by EASA testers is another step in [the certification] direction," says United Aircraft president Yuri Slyusar.
Three MC-21-300s, all with Pratt & Whitney PW1400G engines, are being used for flight tests at the Gromov institute in Zhukovsky near Moscow.
The aircraft has been flown across a spectrum of typical operating conditions up to maximum altitudes of 12,500m at speeds up to M0.89, with durations of 6.2h.
"Performance efficiency of all systems was confirmed in a wide range of speeds and altitudes," says Irkut, adding that air data calibration has been achieved.
The aircraft has undergone tests on angle-of-attack limitation and flutter, determination of minimum take-off speed, and in-flight engine and auxiliary power unit restart.
All three test MC-21s are to be presented during the upcoming MAKS Moscow air show, due to take place in August.
Irkut says a fourth flight-test aircraft, also with PW1400G engines and a passenger cabin, is having its systems installed and will join the fleet this year.