Russia’s first fifth generation fighter, the Sukhoi Su-57, has entered serial production. Under the terms of a contract signed last June United Aircraft Corporation will produce 76 Su-57s, with the first jet likely to enter service before the end of 2019.

First sighted in 2010, the Su-57 takes its name from the famous Sukhoi Design Bureau. The Su-57 was a previously unknown design and its appearance took the West by surprise. The Su-57 is described as a ‘fifth-generation fighter,’ a term referring to the fifth-generation of post World War II fighter jets. Fifth-generation fighter jets typically include a stealthy design, the ability to cruise at speeds of Mach 1 or greater, and powerful radar and the ability to send and receive data with friendly forces in a networked environment.

The Su-57 is technically a multi-role fighter, with the ability to operate in both air-to-air and air-to-ground roles. The fighter will also be a launch platform for the Kinzhal (‘Dagger’) hypersonic missile. Experts believe Kinzhal is a 9K720 Iskander land-based short-range ballistic missile modified to be carried underneath an aircraft. Kinzhal has a top speed of Mach 10 and and a range of 1,242 miles.

But the world’s initial surprise of the Su-57’s existence has been tempered by extensive delays. The aircraft, previously known as T-50, first flew on January 29, 2010. In 2012, the head of the Russian Air Force claimed production of the aircraft would begin in 2015. That never happened. India, an early partner in the program, dropped out after repeated delays, demands that it contribute more money to the program, and a refusal by Russia to share software source codes.

According to TASS, a Russian government-owned state media source, Moscow signed a contract for 76 Su-57s last June. At the time, Russia had only committed to buying 16 of the fighters. United Aircraft Corporation, the parent company of the Sukhoi bureau, somehow made the jet twenty percent cheaper, prompting the larger buy.

The big question is how the Su-57 magically got cheaper. Currently there are nine Su-57 prototypes flying, all powered by the AL-41FM1 engine. The AL-41FM1 generates 32,000 pounds of thrust, and the big Su-57 is equipped with two of them. However, the Su-57 is supposed to be equipped with the more powerful Item 30 engines and reportedly cannot cruise at Mach 1 or faster without them. The Item 30s have proven difficult to develop but the Su-57 finally flew with them in 2017. Does the cheaper price reflect the use of the older, less powerful engines? If not, did UAC cut corners on some other aspect of the aircraft’s design?

Regardless of how capable Russia’s Su-57 is, it will be severely outnumbered by fifth-generation fighters fielded by the country’s potential adversaries. F-35 production is nearing a hundred fighters a year, with the U.S. military ordering 2,400 jets, and even countries such as the U.K. and Japan are buying more than a hundred each.

By 2028, when Moscow’s existing orders for Su-57s will be filled, the US and its allies will field 187 F-22 Raptors and somewhere around 1,400 F-35s.