FFOX SIM
My Dashboard
PERFORMANCE

Understanding Cost Index (CI) in Airline Flight Management

How the Flight Management Computer balances fuel economy versus flight time cost in commercial jet operations.

Published on August 1, 2026 7 min FOX SIM Editorial Team

Cost Index (CI) is a numerical ratio entered into the FMC/MCDU that balances fuel costs against hourly flight time costs (ECON speed schedules).

The Economic Formula

Cost Index = Time Cost ($/hour) / Fuel Cost (cents/lb or kg). A CI of 0 prioritizes maximum fuel conservation; higher CI speeds up the aircraft.

Nota Educacional

Este artigo faz parte da biblioteca educacional FOX SIM e destina-se a fins de estudo e simulação de voo. Para operações aeronáuticas reais, consulte sempre as publicações oficiais (AIP, ROTAER, NOTAM) e manuais aprovados da aeronave.

All articles