How reliable is the new F-35 jet fighter comparative to the existing Harrier jump jets?

The F-35 has not been deployed, and it will be years to develop a database sufficiently large to develop a statistically significant calculation. Historically, the engines used in US aircraft are very high quality (non-military industries generally use "6 sigma quality", the engines are at least 8-sigma). However, with all of the stresses, the reliability is fairly low. Reliability engineers use the statistic "MTBF" (mean time between failure) and, military aircraft have an MTBF of approximately 100-200 hours. By comparison, a laptop computer has an MTBF of approximately 25,000 hours.