MOSCOW, March 26 (Xinhua) -- Russian aircraft manufacturer Irkutsk Aviation Plant said it has completed assembling of the second MS-21 passenger aircraft and its test flight will take place in May, a spokesman of the company said Monday.

The second MS-21 has been transferred from the final assembly shop to the flight test unit for ground and flight tests, said the spokesman.

The beginning of the assembly of the first serial airliners MS-21 is planned for June 2018. Now the subcontractors are making parts, panels and units, according to the schedule, added the spokesman.

Last year, the company said the Russian airline Aeroflot will be the first operator.

The MS-21, also known as MC-21, is a newly designed twin-engine passenger aircraft with a capacity of 150 to 212 seats.

Local news media reported that the MS-21 aircraft is expected to become a competitor to Boeing 737 and Airbus A320.