Abstract: An improved cruise speed control system for commercial jet aircraft is described. The basic control terms for the pitch loop are altitude error, altitude rate and washed-out speed or Mach. The basic control terms for the speed loop are Mach error, Mach rate and integrated Mach error. Other speed loop functions include a gain term which increases at low engine response rates, based on either engine rpm or engine pressure ratio (EPR), to compensate for throttle linkage hysteresis, a versine term to compensate for increased drag in turns, an inner EPR loop for damping the outer speed loop, a variable gain term as a function of Mach error to facilitate changes of commanded Mach, and a switch to disconnect Mach error and Mach rate and to increase the nominal value of EPR during periods of air turbulence.