As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
2 PLUS 40 INTO FLIGHT AT FL340 BOTH FMC'S FAILED CRUISE FL340 FOR 30-45 SECONDS. THEY BOTH RE-BOOTED WITHOUT ANY PILOT INTERACTION AND OPERATED NORMALLY. GROUNDED - YES. NO ACTIVE FMC FAULTS. FMC FLT HISTORY ONLY SHOWING RH FMC FAULT ON LAST LEG. CYCLED RH FMC AND LH FMC C/B, FMC'S OPS NORMAL PER B737-9 AMM 34-61-00.