Commercial Fixed Wing
Confusion
Deviation / Discrepancy - Procedural Other / Unknown
General None Reported / Taken
Equipment / Tooling
Crew advised North Atlantic (NAT) crossing on filed NAT A; but now FL380/M85 not the filed FL350/M85.  Unable (nor the two Chiefs) to get [computer software] to show FL380/M85; it gives multiple lower altitudes.  *I did not release this flight; but assume the dispatcher brought down to cross at FL350 because was running into same thing.  The flight was at FL380 before reaching coast out point.  Why would it not be able to maintain across the tracks?  I could not get M84 to give FL380 on NAT A as well without [computer software] giving lower flight levels.  Therefore; unable to give crew accurate burn as well accurate Critical fuel scenario.  This was not a track jumper; but the hypothetical what if he was filed on NAT B and got NAT A Fl380/M85.  I would not have been able to generate what the aircraft is actually capable of doing.
A Dispatcher is informed by one of his flights that they have been assigned FL380/M85 on North Atlantic (NAT) A instead of FL350. The computer software will not accept this altitude and a flight plan with accurate times and fuel burns cannot be generated.