A Russian PAK FA during a test flight. Wikimedia Commons Just as the US is continuing to develop its latest fifth-generation aircraft in the form of the F-35 Lightning II, Russia has been working steadily toward its own version of a next-generation aircraft.

Unfortunately for Russia, its PAK FA, also known as the T-50, is having developmental issues that put its entire premise of being a fifth-generation fighter into question.

Reporting from the Singapore Airshow 2016, IHS Jane's reports that "Russian industry has consistently referred to the Sukhoi T-50 PAK FA as a fifth-generation aircraft, but a careful look at the program reveals that this is an 'in name only' designation."

This is largely because of a lack of evolutionary technology aboard the plane compared with previous jets that Russia and the US have designed. Indeed, the PAK FA's engines are the same as those aboard Russia's 4++ generation (a bridging generation between fourth- and fifth-generation aircraft) Su-35. Additionally, the PAK FA and the Su-35 share many of the same onboard systems.

And even when the PAK FA's systems are different from the Su-35's, the plane's specifications are still not up to true fifth-generation standards.

RealClearDefense, citing Indian media reports that are familiar with a PAK FA variant being constructed in India, notes that the plane has multiple technological problems. Among these problems are the plane's "engine performance, the reliability of its AESA radar, and poor stealth engineering."

The question of stealth is one of the largest factors influencing perceptions of the PAK FA. In 2010 and 2011, two estimates from individuals close to the program estimated that the plane's radar cross section would be 0.3 to 0.5 square meters, RealClearDefense notes.

A PAK FA during a test flight. Marina Lystseva via the youngster

In comparison, the US Air Force has hinted that the radar cross section of the F-22 is as small as 0.0001 square meters. The F-35's RCS is larger, but it is still minuscule when compared with that of the PAK FA, as it has an RCS of roughly 0.001 square meters.

It is helpful to bear in mind, however, that actual RCS numbers are classified. Neither Russia nor the US has released the actual RCS of its aircraft. Nevertheless, if the estimations are anywhere near accurate, the PAK FA is significantly less stealthy than its US equivalents.

Currently, Russia is planning on purchasing 12 PAK FA, down from an initial order of 52 because of problems with the plane, rising costs, and problems facing Russia's economy.