Perhaps then some other method to determine the speed of the aircraft has to be used...

Although I feel that it is a given that turbine powered aircraft would best suited for absolute speed, perhaps we should not use them as a method of power in this discussion.

What I want to focus on is the aerodynamic consideration of high speed designs, the power source is secondary to the primary consideration at this point.

So lets just look at what makes a speed plane, a speed plane.