...Aerion believes it will be able to operate over the US above Mach 1 with the right atmospheric conditions . Due to the aerodynamics, Aerion also says it will be able to operate efficiently regardless of super or subsonic.

Back when Douglas, Boeing and others were looking at the SST, most were around M 2.5-2.8 for sustained cruise as I remember. They could have targeted a higher mach with resulting higher costs for design, engine, etc but they found the real limiting factor for such a design was not speed but rather turn-around time. It took x amount of time to turn the machine around and thus going .xx faster really didn't pay for the additional complexities.

More doubts arise on this issue, and as Rick pointed out it will require a big rule change to even be possible.

Do you mean wide turning radius at high speed cruise?

While it was not the intention of Gulfstream Flight Test to take a subsonic design to supersonic speeds, the jet did in fact go supersonic. No one would intentionally take a transport category jet designed for subsonic flight beyond Mach 1.00. Subsonic wings are designed using the Navier-Stokes equation and Computational Fluid Dynamics to be just that: subsonic. Supersonic wings designed for non-compressible airflow differ significantly in strength and design. Additionally, on aircraft that do not have an all-moving tail the first thing that occurs at Mach 1.00 is a shock wave forms up at 50% chord on the horizontal stabilizer which negates the effectiveness of any flight control operating behind it. Subsequently, pitch control can be lost.

The GV went to 1.07 Mach during developmental test with an FAA pilot from the Atlanta ACO at the controls. One of the stability tests that is done during "cert " is to simulate runaway trim. In the GV, the aircraft is accelerated to Vc at 51,000 feet (0.86 mach), trimmed for hands - off flight, the trim is then run nosedown for 3 seconds, and then the test pilot is allowed to recover the resulting maneuver. After demonstrating that you can do this point, the FAA is invited to come fly the point themselves and verify it. The FAR requires that neither "exceptional piloting, strength or skill" be required to fly these points - this is the part that the FAA pilots demonstrate best.

On the day when the GV "made the number" the FAA test pilot was in the left seat to verify this runaway trim point. Initially, all went well. The jet was accelerated to 0.86 mach and trimmed for hands-off flight at 51,000 feet. The trim was then run nosedown for 3 seconds. Events began to trend badly when the FAA pilot was told, "You got it, recover." He was reticent to pull back on the yoke at that altitude and speed. As a result, the aircraft quickly accelerated to 0.99 Mach. Seeing this, FAA pilot promptly announced to the Gulfstream test pilot, "You got it!"

We learned that day that the EFIS displays only show 0.99 Mach as a maximum. When the Steely-Eyed Gulfstream Test Pilot pulled back on the yoke - nothing happened. The flight test engineers in the back advised him that their instrumentation was showing 1.04 mach (the real time telemetry streaming to Gulfstream flight test operations was showing 1.07 mach).

The elevators were ineffective because they were operating behind a well established mid-span shock wave on the horizontal stab. The GV has a fully movable emergency stabilizer, but it is not designed for supersonic flight. A good test pilot never does add-on testing, so our SEGTP elected not to use the EMER STAB. He rightly thought, "We are descending. As we do so temperature will increase and with it the speed of sound. If I just hang on the aircraft will go subsonic and I will regain pitch control" - which is precisely what happened in the high 30's.

It is significant to note that while operating above the speed of sound the wing manifested no adverse Mach effects - no roll-off, control "snatching" or pronounced "buzzing".