On 16 June, a message arrives to indicate that if the squadron remains available for operations over France, it must organize a series of training to participate in the defense of British territory within Fighter Command. The pilots are, therefore, gradually being dispatched to No. 11 (RAF) Group for an upgrade on radio and radar procedures for bomber interceptions.
In addition, three new pilots arrive on June 18th from No.5 (RAF) Flying Training School. They are Pilot Officer Sydney J. Madle  and Sergeant Derrick W. Halton  and Olivier V. Houghton . The presence of the latter will be very short since he will be transferred, on 10 July, to No.32 (RAF) Squadron.
 Sydney James Madle. Born on 13 January 1921, in Strood (Kent), he was educated at Sir Joseph Williamson Mathematical School before working for South Eastern Electricity in Rochester. He joined the RAFVR in January 1939 and trained at No.23 (RAF) Elementary & Reserve Training Flying Training School and No.5 (RAF) Flying Training School. He joined No.615 Squadron on 18 June 1940.
 Derrick Wilson Halton (748212). Born in 1939. He worked as a reporter at the Northamptonshire Evening Telegraph, before joining the RAFVR in May 1939. After his training at No.5 (RAF) Flying Training School with the No.45 Course (11 December 1939 – 10 June 1940), he joined No.615 Squadron on 18 June 1940.
 Oliver Vincent Houghton. Born on 19 January 1921 in Foleshill (Conventry). He worked as an aeronautical mechanic, before joining the Civil Air Guard in October 1938 and the RAFVR on 22 March 1939. He trained at No.4 (RAF) Initial Training Wings (30 October) and No.5 (RAF) Flying Training School (9 December). He joined the No.615 Squadron on 18 June 1940, but his presence was very short and he was transferred to No.32 (RAF) Squadron (10 July) and No. 501 ( RAF) Squadron (27 August). He was killed in air combat on 6 September 1940, when his Hawker Hurricane Mk I V6646 crashed near Long Beech Wood (Kent).