AFTER EXITING RWY; ACR FLC DETERMINE THAT THEY LANDED WITHOUT CLRNC. PIC CALLED TWR SUPVR WHO ADVISES THEY HAD NO PROB OR CONCERN. FLC STATE FATIGUE; DUE TO EXTRA LONG WORK DAY; CAUSED BY ACFT MAINT PROBS AND REPOSITIONING OF ACFT TO ANOTHER ARPT.

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