Russia is expected to hold the first test...

"The [test] flight was initially scheduled for Thursday, but has been postponed," the source at the Gagarin KNAAPO company, a subsidiary of Russia"s major aircraft holding Sukhoi, said.

Russia"s only known fifth-generation project is Sukhoi"s PAK FA and the current prototype is the T-50. It is designed to compete with the U.S. F-22 Raptor (so far the world"s only fifth-generation fighter aircraft) and the F-35 Lightning II, but has yet to take to the skies.

The PAK FA is believed to possess advanced avionics, stealth capability, a ferry range of 4,000 to 5,500 km, and endurance of 3.3 hrs; it is armed with next-generation air-to-air, air-to-surface, and air-to-ship missiles, and has two 30-mm cannons.

Russia has been developing its newest fighter since the 1990s. Russian Deputy Defense Minister Vladimir Popovkin earlier said the combat aircraft would enter service with the Air Force in 2015.

MOSCOW, January 28 (RIA Novosti)