The final selection of the engine for the MRCA was made between a new European collaboration, Turbo Union, with the RB199, and Pratt & Whitney who proposed the JTF16.

Rolls-Royce designed the fan using scaled-down Pegasus knowledge, the combustor, the high pressure (HP) turbine and the reheat.

The reheat used cold air combustion techniques, described by Sotheran[5] and which were derived from their experience with ramjets and plenum chamber burning (PCB) in Pegasus front nozzles.

Service flying with the Royal Air Force, German Navy and German and Italian Air Forces in the European environment showed normal failure mechanisms for turbine blades, thermal fatigue, creep and high cycle fatigue (HCF) so development started on replacing the initial production equiaxed blades with single-crystal ones which last longer at high temperatures.

Sand ingestion tests had been done and passed as part of the qualification for service introduction but operating in desert conditions with the Royal Saudi Air Force produced new problems.

"[11] Looking back on the RB199 program in 2002 Chief Engineer for the RB199, Dr.Gordon Lewis, concluded "The final production standard provided satisfactory reliability and performance.