The first two X-43A aircraft were intended for flight at approximately Mach 7, while the third was designed to operate at speeds greater than at altitudes of 30,000 m or more.
Первый вариант X-43A разрабатывался с целью достижения скорости выше числа Маха 7 — около 8 тысяч км/ч (2,24 км/с) на высоте 30 000 м или более.