The P-39 Airacobra was an American World War II fighter aircraft. The novel refers to the P-39 as an AirCobra. During World War II the P-39 was sold to the Russian air force under the lend-lease act. Lieutenant John Kirk was ferrying some of the P-39s to the Russians when he was shot down. Pavel Chekov, who was trapped in this time period, had trained in a P-39 as a member of the air force. (TOS novel: Home is the Hunter)