sentences:  This occasion marked the first time that a British independent airline commenced non-stop transatlantic scheduled services on routes linking the UK and the US.Also on 1 April 1973, BCal replaced the two-letter CA airline designator – which was originally used to prefix all Caledonian Airways flight numbers and continued to prefix flight numbers allocated to transatlantic charter flights until 31 March 1973 – with the BR airline designator it had inherited from BUA at the time of its formation.This resulted in exclusive use of the BR designator as a prefix for all BCal flight numbers.