mckellar was also a keen fitness enthusiast and, despite his short stature, built up a great physical strength. though he enjoyed wine and smoked the occasional pipe or cigar he kept in peak physical shape until his death. even at the height of the battle of britain he was always clean shaven and immaculately dressed. mckellar's spare time was used reading about sport and first world war fighter pilots. his interest in the flying personalities of the past spurred him to take up flying. he joined at his own expense the scottish flying club, which had been founded in 1927; it leased and managed renfrew airport from 1933 until it was requisitioned during the second world war. mckellar quickly acquired a pilot's licence. by the time he began his military career, mckellar was a very experienced pilot, and he soon began earning relatively quick promotions.