Cunningham was promoted to flight lieutenant on 12 March 1940. In April the squadron flew as escort for a De Havilland Flamingo carrying Winston Churchill, First Lord of the Admiralty, to Paris to attend a meeting after the German invasion of Denmark and Norway. Most of the unit's time during the Phoney War was spent in intensive training over the Wash which included co-operation with searchlights and mine-laying operations. On 15 May, 604 relocated to RAF Manston. From the airfield Cunningham flew sorties over the English Channel and patrols over Dunkirk as the Battle for France intensified. Cunningham made no recorded contact with the enemy and France capitulated on 25 June.