Caldwell claimed two kills in his first interception sortie over Darwin, a Mitsubishi A6M Zero (also known by the Allied codename "Zeke") fighter and a Nakajima B5N "Kate" light bomber. The Spitfire pilots found Japanese fighter pilots reluctant to engage Allied fighters over Australia, due to the distance from their bases in the Dutch East Indies. The wing initially suffered high losses, due to the inexperience of many of its pilots, and teething mechanical problems with their newly "tropicalised" Mark VC Spitfires. This was viewed with concern by high commanders, to such extent that the Allied air commander in the South West Pacific, Major General George Kenney, considered sending the wing to the New Guinea campaign, and returning US Fifth Air Force fighter units to Darwin.