In September 1917, Allingham, by then an Air Mechanic First Class, was posted to the Western Front to join No. 12 Squadron RNAS. This unit acted as a training squadron for other RNAS squadrons based on the Western Front. There is also some evidence that the squadron was involved in combat operations. When Allingham arrived at Petite-Synthe, both the Royal Flying Corps (RFC) and the RNAS were involved in the Ypres offensive. On 3 November 1917, he was posted to the aircraft depot at Dunkirk, France where he remained for the rest of the war, on aircraft repair and recovery duties. He recalls being bombed from the air and shelled from both the land and the sea.