The aCC growth cone extends normally through the ISN pathway and reliably selects its normal target muscle in Fas3^HF-ET flies, despite misexpressing Fas3 during axon pathfinding and target selection. SNa innervation is normal in Fas3^HF-ET flies, despite misexpression of Fas3 in the SNa motorneurons during axon pathfinding. Muscle 1 lacks innervation in 4% of cases in embryos carrying both Fas3^Mhc.PC and Fas3^HF-ET. The aCC growth cone stops short of muscle 1 and instead bends its head slightly posteriorly along muscle 2 in 25% of cases in these embryos. Muscle 1 lacks innervation in 12% of cases in embryos carrying both Fas3^Mhc.PC and Fas3^HF-ET and expressing Fas3^hs.PK (which is present in the P{hs-Fas3.K}HF-ET insertion) due to heat shock. The aCC growth cone mistargets muscle 2 in 30% of cases in these embryos. Abnormal axon collaterals stem out of the SNa nerve in 17% of cases in 18 hour embryos carrying both Fas3^Mhc.PC and Fas3^HF-ET. These collaterals are thin, probably consisting of only one or two axons, and misinnervate muscles 12, 13, 26 or 27.