On 26 October MacLachlan was promoted to flying officer, and undertook an attack mission. During the course of the flight his wingtip made contact with the ground but he was able to return to base. The squadron settled down into winter quarters until March when they were reassigned to the French border region with Spain. On 1 April he celebrated his 21st birthday and took the opportunity of driving from Perpignan across the frontier into the Pyrenees to celebrate it. On 9 April the squadron was put on alert when the Germans invaded Denmark and Norway and the squadron were soon relocated to northern France at Mourmelon. On 10 May the Phoney War came to a close with the German invasion of Western Europe.