Plagis's first major operation was Operation "Spotter", the first of many British endeavours to reinforce the besieged island of Malta in the face of German and Italian assaults during the Battle of the Mediterranean. Malta was considered to be of vital strategic importance, and its defence was looking increasingly precarious in March 1942. "Spotter" was a plan to strengthen its British garrison with 16 new Spitfire Mk Vs, which would be carried part of the way from Gibraltar on the aircraft carrier HMS "Eagle", then flown to Malta; the pilots would then become part of the severely depleted No. 249 (Gold Coast) Squadron. The team of pilots comprised eight British airmen, four Australians, two New Zealanders and two Southern Rhodesians—Plagis and his close friend Pilot Officer Doug Leggo.