The P-26 was being replaced by the P-35 and then the P-36 in the late 1930s, but had not been completely removed from USAAC service by the outbreak of war, some were still in service.
By mid 1940 P-40 production had started and these would replace the P-35 and P-36. Later the P-39 and P38 would join the P-40 in service..