The Scottish Saltire and field is one of the key components of the Union Flag . The Union Flag has been used in a variety of forms since 1606 , when the flags of the Kingdom of Scotland and Kingdom of England were first merged to symbolise the Union of the Crowns . The Saltire is one of the key components of the Union Flag which , since its creation in 1606 , has appeared in various forms following the Flag of Scotland and Flag of England first being merged to mark the Union of the Crowns .