I doubt rail will replace cross-country flights, but there is a ton of air traffic on shorter routes.
As one example where it's already done, the DC-NYC Amtrak route is quite popular, despite being just as expensive, if not more so, as the plane ride. It takes a similar amount of time, factoring in travel to and from airports, waiting, etc. and is much nicer. There are still a ton of airline flights between these two cities as well, of course, and those could probably be supplanted to a large degree with additional improvements.
That's with current American trains, which are painfully slow. Imagine modern high-speed rail between, for example, DC and Miami. It's a bit over 1,000 miles which would take about five hours. That would be an excellent substitute for the plane trip, which is about two hours in the air, but tons of time and hassle at the airports. I have family in South Florida and if such a train existed at something like a reasonable price, I'd definitely go for it. As it is, Amtrak on that route takes nearly 24 hours and costs way more than an airline ticket. I don't see why they get any passengers at all, given that.
Seems like 1,000 miles is about the limit for high-speed trains. How many pairs of large American cities are less than 1,000 miles apart and have lots of travel between them? I would bet there are quite a number. Rail doesn't have to solve everything to solve a bunch of things.
I've done a lot of NY->Bos trips. The trains are much more reliable. It's a hair longer on the train, but it's all productive time. On a plan you're lucky to have an hour productive. There's also a NY->Bos overnight.
Chicago to Seattle is something like 40 hours, with almost the same number of stops.. Even with slow trains, the time would be much faster if you didn't have to slow down, stop for a few minutes, and then startup again every time you reached a town of 3000 people.. Its like they've had to put a station in every congressional district :)
If you consider that route pretty bad just consider this:
Kentucky and TN do not have Amtrack. [Well TN has a small segment on its western side that goes N to S but its pretty much a desert.
This means that if you wish to go from ATL, Raleigh/Durham, etc to Chicago, you have to make "connections" (good luck making that on amtrack) in either Charlottesville VA or DC. After that it is still 24 hrs at best.
Kentucky used to have Amtrak, the Kentucky Cardinal. It went from Louisville to Chicago and took what felt like 12 hours although not sure I'm remembering that correctly. It was only $30. I had high hopes for that route, that it would open up more options to travel by rail from my hometown.
The problem with that was that the short line from Louisville to Indianapolis hasn't been seriously updated in over 50 years. The speed limit on the entire section of track is something like 30 mph. Of course folks aren't going to go by train when it's over twice as long as driving.
There's been some talk of a Louisville-Lexington-Nashville line, but nothing particularly likely to happen.
You doubt rail will compete/replace cross country air travel because "it seems like 1,000 miles is the limit for high speed trains." Is there any reason to think that what appears to be the case is actually the case? I do not know a lot about rail travel why is distance a limiting factor? Is it a business limitation or a physical limitation?
The 1,000 mile rule is pretty widely quoted and is not too controversial. Reasons for it are:
1. Speed (physical limitation). Due to reduced overhead (time getting to and at airport), trains are faster or equivalent to air travel for short (<500 mi) routes, and are not much slower for medium (<1000 mi) routes. Whereas for cross country (~3000 mi) routes, even a high speed train would take a couple of days for a trip that could be made in 10 hours by plane (incl. overhead).
2. Infrastructure costs. Air travel infrastructure is proportional to the number of passengers and constant with respect to the travel distance (since each passenger occupies 1/200th of a gate at two airports for about an hour, regardless of the travel distance. Rail travel infrastructure is proportional to the distance traveled and relatively constant with respect to the number of passengers. These combine to mean that shorter trips with more passengers are more competitive by rail, and longer trips with fewer passengers are more competitive by plane.
1,000 miles is about the point where air travel starts to become substantially faster than modern high-speed rail.
Airplanes add about three hours onto the trip just to account for getting to and from the airports (which are almost always far away from the city), going through security, arriving early enough to account for unexpected problems, etc. With trains it's much less, often well under an hour.
However, airplanes go much faster. That DC-Miami trip would be about five hours by high-speed train and is about two hours by plane. It would be roughly a wash when you account for the extra overhead of airplane travel, making the train more attractive due to being more comfortable and potentially cheaper. But go much farther, and the plane starts to get a lot faster. For a coast-to-coast flight, a high-speed train is still going to take nearly a full day, while an airplane can do it in about eight hours after accounting for the extra overhead.
So, as far as I can see, 1,000 miles is roughly the breakeven point on planes versus high speed rail.
As one example where it's already done, the DC-NYC Amtrak route is quite popular, despite being just as expensive, if not more so, as the plane ride. It takes a similar amount of time, factoring in travel to and from airports, waiting, etc. and is much nicer. There are still a ton of airline flights between these two cities as well, of course, and those could probably be supplanted to a large degree with additional improvements.
That's with current American trains, which are painfully slow. Imagine modern high-speed rail between, for example, DC and Miami. It's a bit over 1,000 miles which would take about five hours. That would be an excellent substitute for the plane trip, which is about two hours in the air, but tons of time and hassle at the airports. I have family in South Florida and if such a train existed at something like a reasonable price, I'd definitely go for it. As it is, Amtrak on that route takes nearly 24 hours and costs way more than an airline ticket. I don't see why they get any passengers at all, given that.
Seems like 1,000 miles is about the limit for high-speed trains. How many pairs of large American cities are less than 1,000 miles apart and have lots of travel between them? I would bet there are quite a number. Rail doesn't have to solve everything to solve a bunch of things.