his flying skills earned him the attention of lord clydesdale, commanding officer of no. 602 squadron aaf. clydesdale invited mckellar to join the auxiliary air force (aaf) and was soon commissioned into the raf as a pilot officer on 8 november 1936, joining no. 602 (city of glasgow) squadron raf. mckellar's comrades affectionately nicknamed him "shrimp" owing to his short, , stature. mckellar stayed with the squadron and on 8 may 1938 was promoted to flying officer.