Maintenance-free operating period (MFOP) is an alternative measure of performance to the mean time between failures (MTBF), defined as the time period during which a device will be able to perform each of its intended functions, requiring only a minimal degree of maintenance. It was originally proposed in 1996 by the United Kingdom's Ministry of Defence, with intended application to military aircraft.
^Dinesh Kumar, U.; Knezevic, J.; Crocker, J. (1999). "Maintenance free operating period – an alternative measure to MTBF and failure rate for specifying reliability?". Reliability Engineering and System Safety. 64: 127–131. doi:10.1016/S0951-8320(98)00048-9.
^Chew, Samuel P.; Dunnett, Sarah J.; Andrews, John D. (2008). "Phased mission modelling of systems with maintenance free operating periods using simulated Petri nets". Reliability Engineering and System Safety. 93 (7): 980–994. doi:10.1016/j.ress.2007.06.001.