On 22 September 1914 Collet, flying a Sopwith Tractor Biplane, led a raid by four aircraft, which flew two hundred miles to attack the Zeppelin sheds at Düsseldorf and Cologne, in the first British air raid of the war. Thick mist in the Rhine Valley meant that only Collet found his target, and he accurately dropped two bombs from on the shed at Düsseldorf, although the bombs failed to explode. Despite being hit by enemy fire, he returned safely, as did the other three aircraft; they had spent more than an hour flying over Cologne attempting to find their target, but after failing to do so they returned to base without dropping their bombs.