Both Mhc^R672C hetero- and homo-zygosity in a Mhc¹⁰ background leads to a fully flightless phenotype; the Mhc^R672C homozygosity condition also typically leads to a wings-up phenotype.

In the Mhc^R672C, Mhc¹⁰ double homozygosity condition, pupal indirect flight muscles display severe assembly defects (abnormally shaped and sized myofibrils, and aberrantly localized Z-band material, with poor myofilament organization); 2h-old adult indirect flight muscles show extreme disruption in morphology (thick filaments dispersed in myofibril remnants and reduction in regular sarcomere patterns); these defects become more severe during adulthood. In the Mhc^R672C/+, Mhc¹⁰/Mhc¹⁰ condition, pupal indirect flight muscles show no obvious defects; however, 2h-old adult indirect flight muscles present myofibrils with disrupted myofilament arrays and branching sarcomeres with wavy Z- and M-line material; 2 days-old adult indirect flight muscles show disrupted myofibril morphology with scattered Z-band material, and sarcomeres are further disordered; in 7 days-old adults there is a severe muscle degeneration.