India, July 28 -- Russia's Sukhoi Su-57, billed for two decades as Moscow's answer to America's F-35 and the centrepiece of its claims to fifth-generation air power, has suffered a cascade of losses, near-misses and self-inflicted wounds that have left analysts questioning whether the aircraft that was meant to project Russian technological prestige can survive a war it has rarely been allowed to fight in.

The latest blow came on July 23, when Russia lost an Su-57 in circumstances that remain disputed even among Russian military bloggers. The Russian Ministry of Defence issued only a brief statement referring to the crash of a "combat training aircraft during takeoff," without specifying the type or the cause, according to reports.

Russ...