COMBINED ENVIRONMENT RELIABILITY TESTING (CERT) has been completed for a military and commercial jet engine mounted digital electronic fuel control application. CERT testing has revealed several failure modes not normally identified by traditional development, qualification and burn-in testing. This paper discusses the manifestation and corrective action of these failure modes and identifies several secondary anomalies that were discovered during repair actions or deliberate inspections. These anomalies, although not directly responsible for a control malfunction, could eventually have caused a control removal.CERT tests on two different engine controls have highlighted meaningful comparative results that tend to verify initial reliability predictions. Analysis of test data has also indicated potential improvements in future CERT testing to yield more cost effective results. Lastly, this paper presents the benefit of real time CERT testing by virtue of excellent propulsion control reliability being realized by airline revenue service.