Boeing FMC RTA
Recently we were given a crossing time at a waypoint further along in our flightplan. This was entered as an RTA on the Progress page. Prior to reaching that waypoint ATC asked us if we could accept a higher altitude. There was no OPT or Max altitude to be found in the FMC. On a hunch I deleted the RTA time(and executed) and the two altitudes were displayed again. This feature was later found in an FMC guide that I have. Anybody know why this is in the FMC?.