The NBAA Forum for Enhanced Reliability and Maintainability Standards (FERMS) provides a framework for measuring the reliability of business aircraft. Two strict formulas and definitions describe these measures in terms of dispatch reliability and operational availability:

Dispatch Reliability is the percentage of scheduled departures that do not incur a delay, cancellation, turn back or diversion.

Operational Availability is a measurement of the percentage of time the aircraft is available for flight. It is defined as the ratio of time that the aircraft is available divided by total time, in hours.

To use the formulas, operators enter relevant maintenance events for their aircraft, tracking the number of flight hours and landings at the time of each event. The resulting data will help validate product-selection decisions and better manage operationally controllable elements.

Download the PDF resource for more information, including clarifications and guidelines to help you make best use of the formulas within your operation.

Download the FERMS PDF Resource (1.3 MB, PDF)