The
single-letter signal means, ‘My vessel is healthy and
I request a free pratique’. The Q flag is flown on entering a foreign port, or
returning home from abroad. The ‘pratique’ that is requested is ‘permission’
or ‘licence’ to come ashore. It may relate to health,
customs or immigration rules. Hence the association of Q and quarantine. In the
phonetic alphabet the word is Quebec, pronounced in the French manner as if
spelled Kebek.