Irkut has commenced the next phase of flight-testing with the MC-21 after a hiatus of several weeks.
The initial aircraft performed nine preliminary test flights, beginning on 28 May, before being parked for assessment and modification work.
Irkut states that the MC-21 embarked on a second stage of testing on 13 September with a 2h sortie.
"The modified aircraft systems worked without problems during the flight," it says.
Since the first phase of tests Irkut has fitted strain gauges to the airframe in order to monitor structural loading.
Irkut says the aircraft has also undergone updates to its system software.