Narrative:

At cruise altitude after 30 minutes of flight; we experienced a simultaneous loss of both FMC's. The left FMC and right FMC failed to function. Indications included the following. Left navigation display went blank with 'map' flag; 'vtk' flag; FMC P/rst. White 'a/T-lim' illuminated at top of primary engine display along with green dashes for each engine limit above the N1 displays. First officer's navigation display was visible; but only as something to look at for overall situational awareness. We could not operate either FMC/CDU except for limited ACARS functions like requesting ATIS. We could not access the legs page; fix page; departure arrivals page or any other navigation type function in either box. If you tried to select the 'legs' page; the CDU screen would blank on each box for about 3-4 seconds; then the menu page would pop up with three options. ACARS; acms; and hgs modes would display. We were unable to couple the working autopilot to any type of navigation mode. This required the use of heading select for the duration of the flight. We decided to find a suitable airport that we could divert to with VMC conditions both enroute and at the field. ZZZ was the best choice for this with clear skies; and no weather issues after we cleared the line that was along our original route. We notified ATC early on to get a climb out of the weather; and icing that we were in while we worked to troubleshoot the issue. We appreciate the outstanding support we received from washington center and others as we worked through this event. Outstanding work by my first officer must be recognized as we worked through this event together.

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Original NASA ASRS Text

Title: 737 Captain reported multiple Flight Management System failures at cruise altitude.

Narrative: At cruise altitude after 30 minutes of flight; we experienced a simultaneous loss of both FMC's. The left FMC and right FMC failed to function. Indications included the following. Left NAV display went blank with 'MAP' flag; 'VTK' flag; FMC P/RST. White 'A/T-LIM' illuminated at top of Primary Engine display along with green dashes for each engine limit above the N1 displays. First Officer's NAV display was visible; but only as something to look at for overall situational awareness. We could not operate either FMC/CDU except for limited ACARS functions like requesting ATIS. We could not access the Legs page; Fix page; Departure Arrivals page or any other NAV type function in either box. If you tried to select the 'Legs' page; the CDU screen would blank on each box for about 3-4 seconds; then the Menu page would pop up with three options. ACARS; ACMS; and HGS modes would display. We were unable to couple the working autopilot to any type of NAV mode. This required the use of heading select for the duration of the flight. We decided to find a suitable airport that we could divert to with VMC conditions both enroute and at the field. ZZZ was the best choice for this with clear skies; and no weather issues after we cleared the line that was along our original route. We notified ATC early on to get a climb out of the weather; and icing that we were in while we worked to troubleshoot the issue. We appreciate the outstanding support we received from Washington Center and others as we worked through this event. Outstanding work by my First Officer must be recognized as we worked through this event together.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.