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Well, 24 knots is about 28 miles per hour. Listed top speed is 24 knots, so she will probably do 28-30 when necessary...in a pinch, maybe a little more.

I know that the nuclear carriers, which are listed at 30+ will do over 45 for short periods if necessary...like to avoid a torpedo...or outrun it.

They will flat leave their escorts behind if they have to, because all of them are non-nuclear these days and they are listed at 30 knots but can max out at 38 or so.

I didn't know of any specific time limits as to how long we could run all out flank. But I remember times we ran it well over 24 hours and ran just slightly below it all the way from Rota to Norfolk. We also ran through the Straits of Messina one night several times at Flank practicing anti-sub maneuvers. I would estimate the speed that night at about 60 mph. I didn't get to go into Central or down to Fwd IC room for a look see at the readings LOL. But I was looking at land and lights that night.

No one had too tell us we were running flank you could feel and hear it especially on the second deck. Usually underway unless you were down in number one pump room in the bow you would not feel the rise and fall. You'd only notice port to starboard listings. At Flank you'd feel the ship going up and down.

My last trip back from the MED we were flat out hauling. It's been 33 years but IIRC there were concerns about us getting across and ahead of a major storm {hurricane} well too our south. I remember because even though we were a long ways from it we were in some very rough seas. We were also tossing everything not bolted down over the side. Two reasons for that. One was the storm the other was we were scheduled to head into a year long overhaul and they wanted as much stuff off the ship as possible for that.

The new America does have a much lower speed. But the speed gets the job done. If you want to drive from NYC to LA fast you want a fast car. If you want to haul freight or equipment from NYC to LA it takes a truck. Slower speeds but it will get there. The old LST troop and amphib equipment haulers {Tank Landers} did much less than that somewhere like 14 knots and they served us through Nam.

I know that the nuclear carriers, which are listed at 30+ will do over 45 for short periods if necessary...like to avoid a torpedo...or outrun it.

The nuke carriers, with the exception of Enterprise (more on her in a moment) are actually slower than the old conventional carriers of the Forrestal/Kitty Hawk/JFK classes.

Reason is a combination of hull optimization and available shaft horsepower (SHP). Having a nuke plant really doesn't convey any sort of mystical capability on a ship, other than being a way to boil water into high-pressure steam for a couple/few decades at a time. That steam still needs to be channeled into the turbines, which are the limiting factors in a nuke carrier design. And the nukes have pretty much the same SHP rating as the conventional CVs did (Forrestfire had an older plant design, so slightly less SHP than the followon ships did).

So engineering plant capability (as measured in SHP) being equal, top speed was a matter of hull design. The conventional CVs were optimized for a sub-flank (so 25-27 knot) cruise capability to extend their range. This gave them a hull that could allow flank speeds above 31/32 knots ... so long as the captain was willing to burn off all their fuel in relatively short order.

Given the functionally unlimited (25 year cores) fuel supply, the Nimitzes' cruising speed IS their flank speed. So there was no need to optimize the hull for slower but more fuel efficient cruise. This led to a fuller hull form to squeeze in extra fuel, ordinance, etc. But the fuller hull also gives them a slightly slower speed. Apparently (there was an engineering analysis covering all this posted out on the internet years ago) the later Nimitzes (which outweigh their earlier sisters by about 10,000 tons) are barely able to reach 31 knots.

Now, the promised note about Enterprise. She's a one-off prototype/proof-of-concept. One hell of one, given that she's being retired at 50 years after having had an initial design life of 25. She was designed on a modified Kitty Hawk hull extended to squeeze in her 8 reactors (Nimitzes only have two of those) - which was pretty much a direct order from Hyman Rickover who wanted her to have as many reactors as the CVs had boilers (in retrospect, Enterprise only needed six reactors and the other two create steam well in excess of requirements).

So Enterprise got the best of both worlds; a hull form with a slightly better length to width ratio than the Kitty Hawks upon which she was based (and significantly better than the Nimitz design), with an unlimited fuel supply. Even with all that tho, the laws of physics still apply and the most reasonable estimates place her top speed at around 33.5 knots. Which she can run at until either the plant starts breaking down from physical stress, or the cores get depleted.