The risk of Luftwaffe attack on training bases in Great Britain coupled with the urgent need for larger numbers of well trained aircrew than the pre-war systems could produce brought about the British Commonwealth Air Training Plan (BCATP), often referred to as simply "The Plan" [REF].
On completion of basic military training aircrew candidates would wear a white flash on the front of their service issue "side caps" denoting their "aircrew under training" status.