 01-60J-18 dated 8 April 1944 and a dorsal fin should be installed.Dorsal fin kits are being made available to overseas activities"
The dorsal fin kits became available in August 1944, and available as retrofits for P-51Bs and P-51Cs (but rarely used on the "razorback" -B and -C Mustangs), and to early P-51Ds and P-51Ks that had not already been built with them.Also incorporated was a change to the rudder trim tabs, which would help prevent the pilot over-controlling the aircraft and creating heavy loads on the tail unit.