B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Weather / Turbulence
General None Reported / Taken
Aircraft
Took off out of MCO and climbed to FL280 where there was a bumpy ride. We checked to see if we could climb because of bumpy ride. Our max altitude was FL358. We climbed to FL340. After being at cruise for a while we noticed the airspeed would not go above .76. We looked at the cruise page and noticed our max alt was now FL328. We descended to FL320. After leveling we noticed our max alt was now FL268. We consulted with dispatch and maintenance and our charts. There appeared to be an anomaly. After a period of time the FMC appeared to operate normally. We closely monitored the airspeed the entire time and were never within 20 knots of buffet even though we had a buffet message at one point.
B737NG First Officer reported noticing indications of a malfunctioning FMC; including inconsistent maximum altitude indications.