Raytheon is qualifying Norway's NAAMO as a second source for the rocket motor of the AIM-120 AMRAAM after experiencing "some difficulties" with supplier ATK.
Anybody remember the Great Engine War?
Pratt & Whitney's early struggles with the F100 powering the F-15 and F-16 prompted the US Air Force to launch the General Electric F110. It's an example that has been invoked by supporters of the General Electric/Rolls-Royce F136. The key difference is that the Pratt & Whitney F135 has not faced struggles F-35 while in operational service, which remains at least seven years away.