From the moment I entered the planned step climb of FL370 from my beginning cruise altitude of FL350 of my 1800 mile flight from KSEA to KFNT, the FMS cruise page stated that this altitude was 'unable'. I tried reentering it later in the flight. Still unable, even when the cruise page displayed an optimum altitude of FL374 and, inexplicably, a maximum altitude of FL371. Any ideas?

See http://forum.avsim.net/topic/344463-step-climb Post #15 in particular.

Thanks