My comment was about the fact that if you are taking off from a land locked city, you have to wait till you are over the ocean before going supersonic. So there

My comment was about the fact that if you are taking off from a land locked city, you have to wait till you are over the ocean before going supersonic. So there is more time just travelling at regular speed. With New York, Toyko, London etc you only travel a short distance before you can speed up and create the sonic boom.