Why's it called a Commonwealth aircraft CA18 rather than a North American P51
P-51 was the designation given to the aircraft by the USAAC. The British were the instigators for the design and development, and giving the aircraft the name "Mustang". They referred to the aircraft as a NAA "Mustang" followed by the mark number eg Mustang IVa.
The P-51 designation could only be applied to an aircraft that had been produced to a USAAC order, and duly assigned a USAAC serial, which may then have then gone to another military operator under the lend lease program.
Australia operated them all - home built CAC 17 & 18, USAAC lend lease, and British aircraft of various marks supplied under lend lease. Australia was unique in that the CAC 18 Mk. 23 used versions of the Merlin not used by any other operator in their Mustangs.
In 1948, the designation P-51 (P for pursuit) was changed to F-51 (F for fighter). So the US didn't have any P-51's in Korea.
