As Air Pig indicated, there were two main career paths for pilots in those days. The Supplementary List, in broad terms, offered a career to age 38 or 16 years service but with limited promotion prospects. The General List offered a full career to age 55. It was made up of ex Cranwell cadets plus Supplementary List officers who transferred to the General List by way of a yearly competition. They were often given the more demanding ground tours and it was expected that from among them would emerge officers of the highest ranks. There may also have been a few short service commissions available in the days of the Javelin.
So, refererence to 'career pilots' almost certainly means those on the General List.