Date: 202201
Location: ZZZZ.Airport, FO
Flight conditions: VMC
Aircraft: B777 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise; Parked
ATC / advisory: Center ZZZZ
Aircraft component: Data Processing
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Troubleshooting; Workload; Human-Machine Interface
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Detector: Person Flight Crew
When detected: Pre-flight
Result: General None Reported / Taken
Contributing factors: Software and Automation; Company Policy; Aircraft
Primary problem: Software and Automation

Narrative: After flying from ZZZZ to ZZZZ1 and preparing to return to ZZZZ; We learned that the entire data link system for the airline had been down for 1 hour; and would stay out for an undetermined amount of time. Apparently; this was night 1 of three days that the system was to be purposely down for maintenance of some sort. While the timing worked well for the US/domestic operation (middle of the night); it was right in the middle of the day for the [foreign] operations. The aircraft would not 'Auto Initialize'; which of course; begins the sequence of automatic data links to the aircraft. After a crew discussion; the consensus was to manually input the route.The entire crew was present; and coordinated the correct loading of the route. It was then discussed; that the weights would not data link; as well as any performance information. Ultimately; we were shut down until the data link came back up. Eventually; the system slowly returned; but in a very reduced capacity. The auto init function was utilized; as well as all the performance information: the predicted takeoff data; final weights; and final takeoff data. As a side note; the flying FO (First Officer); did the load at the gate; and the final load after engine start. After a normal takeoff and climb; FO went to crew rest; as he was the Flying Pilot. FO relief pilot took the right seat. Near the fir boundary; at cruise altitude; the Center Controller told us that the ADS-B info did not match our flight number. The language barrier was significant; as this was not a typical ATC conversation; and several attempts were made to confirm what the problem was. After investigating several areas where we may have had a disconnect; I believe that we realized the flight number that would normally have data-linked to the route page was empty. We then consulted the [stored information] to determine the correct format for that input. Initially; I believe we input Aircraft Y; rather than Aircraft X. After the flight info was input; we received no other notification of the flight number mismatch; and assumed that the problem had been corrected. It is my understanding that was the case. In any case; the system reset caused us a great deal of trouble; both here and three days later when conducting the last flight of the trip pairing. Automation is a sensational thing when it works correctly.




Synopsis: B777 Captain reported having problems with the aircraft data link resulting in their flight number not matching with Foreign ATC displays.