Do you think that supersonic flights go supersonic within seconds of takeoff? By the time they get to cruising altitude, planes that takeoff from JFK and EWR wi

Do you think that supersonic flights go supersonic within seconds of takeoff? By the time they get to cruising altitude, planes that takeoff from JFK and EWR will be well outside of NYC. The problem is that the great circle route from either JFK or EWR to Europe basically follows the Northeast Corridor to Boston.