How long is the flight time from Boulder, Colorado to great britain?

Assuming you meant

• Boulder, the Home Rule Municipality that is the county seat and most populous city of Boulder County, Colorado, in the United States and the United Kingdom of Great Britain and Northern Ireland

Did you mean?

• Boulder, the county seat and most populous city of Boulder County and the 11th most populous city in the state of Colorado and Great Britain (The largest island of the British Isles. It includes the countries of England, Scotland and Wales. Together with Northern Ireland it makes up the United Kingdom.)
• Boulder County, Colorado, in the USA and The United Kingdom of Great Britain and Northern Ireland (commonly known as the United Kingdom, the UK, or Britain), the sovereign state located off the north-western coast of continental Europe
• Boulder County, the sixth most populous of the 64 counties of the state of Colorado of the United States and Great Britain (informally Britain), the island situated to the northwest of Continental Europe