How fast can a passenger plane travel 3,000 miles (across the USA)?

I saw a story today about the test of a ‘scramjet’ drone that is projected to fly at somewhere in the neighborhood of Mach 6. There are some other articles around giving even higher speed potential, and some mention it can reach this speed in ‘seconds’. Still more note that in it’s present launching mode (off the wing of a B-52) it accelerates to something like Mach 4 using a solid rocket booster, and its own engine doesn’t turn on until then. So it may be that ‘seconds’ isn’t nearly as impressive as it seems.

All this aside, there is a mention in the link about some hazy future possibility of transferring the technology to civilian transport, and that a plan at this speed could cross the country in less than an hour.

But could it? I’m not asking in terms of technology but in terms of human bodies to cope with it? How many G forces can the average commercial passenger take, being pushed back into the seat early on, and held onto the seat with straps during deceleration? Clearly, no one can get up for a bathroom break or just to walk around, even under mild (less than 2 g maybe?) acceleration in either direction.

Does anyone know what the forward acceleration of the Concorde was while it was revving up to max? Did it have to decelerate at a slower rate than it accelerated, for passenger comfort? Did the pilots deliberately keep the plane’s acceleration down, for the sake of passenger comfort?

The question I’m looking for ideas about is – ignoring things like fuel use, sonic booms and ozone layers – how fast can you get passengers across the country without locking them to their seats, risking some heart attacks, etc. for the whole flight? The planes need to to travel at relatively normal aircraft at both ends so they can work into the traffic plan.

Obviously, the faster the plane can reach cruise speed, the sooner passengers have some freedom of movement. But that has to conflict with health risk for more elderly and infirm passenger. So, do you require passengers to pass a physical, or do you restrict acceleration to what the average grandparent can take? And if so, how long does it take to get to max speed, and how long can you stay there before hitting the brakes?

Yeah, questions like that…

Typical commercial airliner accelerates down the runway at 0.2-0.25 g’s. 0.25 g’s is 5 MPH per second; fourteen minutes of that will get you up to Mach 6 (about 4200 MPH), and another 14 minutes at the end of the flight will bring you back down to zero again.

For the Concorde, Wikipedia lists the thrust-to-weight ratio at 0.373, so presumably it could accelerate at 0.373 g’s. Not clear whether they did that on the runway, or whether the high thrust was reserved for Mach 2 flight.