Nonstop train from Rome airport to Florence

That train is not nonstop. It makes two stops in Rome. It doesn't require any changes.

As to why it's not available, I don't know.

Thank you that is what I meant. I have edited my post to reflect that it's the train with no changes.

I'm not seeing tickets for that particular train being available the entire month of March & April and into May: didn't check beyond May 6th.

Editing: reference this previous thread as this is probably the issue:
https://community.ricksteves.com/travel-forum/italy/rome-to-florence-via-train-51512af9-6a3f-40af-9680-632c95b00ee9

From Florence resident lachera:
"At some times there could be a couple direct trains per day from FCO to Florence, but do not count on it. For example I am now looking for connections on the Trenitalia web site with a sample date (Jan. 8th) and I can't see any. The way tracks are laid at Roma Termini, a direct train has to cross from the northernmost track to the southernmost or vv. entering or exiting the station, effectively blocking the traffic to/from all destinations for a couple of minutes. You can have it once or twice but not two times per hour during all the day. This is why a steady direct service is not planned, only occasional trains."

"I suspect the reason is the technical one I already explained: if there is dense train traffic at Termini, there is no space/time for direct services FCO to Florence and vv. You would have to route trains through Tiburtina and bypass Termini. Terminal stations slow down railway traffic; not only because trains have to reverse direction (10 minutes stop instead of 2-3), but because often entry/exit itineraries are conflicting and you can't move too many trains at the same time. The same problem is at Firenze SMN; trains to/from Bologna interfere with trains to/from Rome and vv. - in Florence they are building an underground railway bypass with a brand new high speed trains station to bypass SMN."

Well that explains it. Thanks, lachera: I'd forgotten that thread.
As previously mentioned there's some work on Tiburtina-Ostiense section during some of that time that could be contributing to some of the problem.

If you search the forum there is a long explanation on why the airport to Florence train rarely runs and it has to do with the dull logistics of it crossing all the tracks because of the direction of travel and causing disruption. Because of this it is an easy train to disrupt and is sounds like it won't be running on April 15th and for at least a few weeks beyond there.

Is your concern them having to change trains in Roma? Is this just a problem you would rather avoid or do you think they are likely to have an issue negotiating their luggage and a train change in Roma Termini? The "Leonardo Express" airport train should come in close to the departure trains to Florence so it shouldn't be a large distance but without the single no change train they will need to change including luggage.

They generic advice is wait until you're on the ground and buy the next fast train tickets to Florence - the app being the easiest way to do this. If you think your parents may struggle with this then that is a concern. Trenitalia does offer and assistance service called Sala Blu and being "elderly" is one of the criteria for getting help which might be worth thinking about if you're really worried.
https://www.rfi.it/en/for-persons-with-disability/information-about-the-assistance-of-the-sala-blu-in-one-click.html

I don't know what kind of assistance is available on the airport side. It's been a while but I remember the airport terminals and the train transfer being longer and more complicated than the Rome train station transfer which is actually pretty compact.

I don't know if it might be worth considering getting them private transfer from Rome to Florence. It won't be cheap but they'll be accompanied the entire way and it's essentially curb to curb.

I may be blowing your concern out of proportion but hope that helps,
=Tod

The "Leonardo Express" airport train should come in close to the departure trains to Florence so it shouldn't be a large distance but without the single no change train they will need to change including luggage.

The airport train arrives at one extreme side of Termini, and it may be quite a walk to the departing train to Florence. If your parents are planning to manage this trip on their own it should be safe to assume that they have minor or no mobility issues, can manage their luggage, etc. Are they experienced travelers?

Both Trenitalia and Italo offer frequent high speed trains from Termini to Florence - you can think of it as a shuttle. So in their case it might be best to wait until they arrive to purchase the long distance tickets, as you won't know how long it will take them to get to the airport train station and then on to Termini.

Have them watch several YouTube videos showing how to navigate both FCO and Termini, and how to travel by train in Italy, if they haven't done so before.

Keep it simple. Do not buy any tickets in advance because it is not needed. Second, if travel date is 15 April, you probably have missed the discount windows. After they have landed and have cleared immigration and customs, proceed to the train station ticket office. Signage and directions are easy to follow. At the station buy a Leonardo Express ticket to Termini (Rome) and from Rome to Florence. The ticket agent will speak English. Personally I would allow at least an hour between arriving at Termini and departure to Florence. Maybe even an hour and a half. Freshen up in the restrooms, maybe have breakfast, buy a picnic lunch for the train and maybe walk outside the station for a quick look around. The is no rush. Something like 50 trains a day between Rome and Florence.

The reason you don't buy at ticket in advance is it not possible to forecast when you would get to the train. We have flown into Rome maybe a dozen times and eight went smoothly. One was a disaster taking over three hours to clean immigration -- too many planes, two few officers. It is not worth the ticket savings or the frustration of dealing with long lines or other unexpected delays.

But another key is to make sure their luggage is reasonable and easy to handle. We get by very well with two rolling, carry on size bags plus two medium to small backpacks. Just go with the flow and don't set time deadlines that could be hard to meet.

We always did what Frank suggests. You can buy your ticket to Florence at the FCO station. If there is a direct train they will sell you that, otherwise a ticket to Termini and the next train to Florence you can reasonably catch. No worry about late planes or early planes.

Note that the platform for the Termini Express is in a different part of the terminal from the platforms for the distance planes.

Because we haven't heard back from the original poster I wanted to clarify my statement:

The "Leonardo Express" airport train should come in close to the
departure trains to Florence so it shouldn't be a large distance but
without the single no change train they will need to change including luggage.

@markcw was right to point out that there are walking distances involved here. What I was saying is that airport trains come into Roma Termini on track 24 (or occasionally on track 23). The trains for Florence will be leaving from the same platform from a different track such as Track 6. Anyone making the transfer will need to walk from the train to the platform, to the appropriate track, and then to their carriage which is shown on their ticket.

What I was trying to say is that this is just a standard train transfer in Italy. The airport train does not arrive in some other place in the train station so there is no navigating the Roma train station at large. They will just need to walk from track 24 to find track 6 and they are laid out in order. And because they are on the platform they won't need to negotiate security, gates or show tickets or anything else.

If mobility is an issue then I would return to my point about Sala Blu or another means of transportation. If you are just trying to keep it as simple as possible for them this transfer in Roma is a typical Italian train transfer despite the size of the station.

Hope that clears up any confusion I may have caused,
=Tod

Thank you all for the helpful responses.

I will look into the Sala Blu service for sure. I might wait to buy tickets just to see if the Frecciarosa 9423 tickets open up, otherwise will buy the Leonardo Express to Roma Termini and then a high-speed train onwards to Firenze. I would much rather purchase these tickets in advance for my parents than have them deal with it. My husband and I are meeting them in Firenze and can take it from there.

Thank you so much!

Last time we took the TerminiExpress it arrived in an entirely different area from the main platforms and was a long walk and a bit confusing. Apparently that is no longer so, which makes it even easier. It is easy to transfer among the trains in the main platform area. And of course many people on the train will be making that transfer.

We usually take taxis from the airport to wherever we need to go when we're coming off an international flight, but based on other comments about how easy the Leonardo Express is, I decided to try that on our last trip since there was just two of us and an EU flight (we arrived from Amsterdam on KLM).

The Leonardo Express was a giant PITA. It was a very long walk from getting out of the secure area to the train, and required taking an elevator where we found a line with over 100 people (for an elevator that maybe held 5-6 people depending on how much luggage they had). We were going to just take the stairs but after hauling our butts and bags up, found the access door at the top was locked. Back to the end of the line for the elevator. Once we made it to the train, it was packed so full that we could not move our feet for the entire 30+ minute ride to Termini (with several stops and starts along the way). We stood in the aisle next to the train door way too up-close-and-personal with the teeming masses. Never again. Even with two of us, we'll take the chance on a taxi getting us to Termini in a reasonable time and for only slightly more than the Leonardo Express.
Now, I agree that the majority of the time this likely doesn't happen, but if your parents are mobility challenged or you just don't want to take any chances, you might consider springing for a taxi or private transfer. It's really a small price in the grand scheme of an international trip.

My wife and I (in our 60s) did what your parents are planning. Signage for the Leonardo Express is very easy to follow, even while jet lagged. We used escalators to access the airport train stations; no stairs to climb and did not wait for an elevator. The airport train station had many customer service personnel ( identified by vests) who spoke English. We took advantage of the Tap and Go feature to purchase our fare. We went to the far right turnstile and tapped our credit cards to pass through. Not ticket machines to maneuver. We did need to separate cards, however. Station personnel directed us to the track for the next train to Termini. Yes, it is like a refugee train; it is packed. We got on early, got a seat but the late comers did stand. Its only 30 minutes or so. We killed and hour in Termini - its crowded - drinking coffee and using the spotless restrooms - 1 euro and they do take credit cards! We rode on Italo to SMN.

I was a little nervous before the trip but I'd do it again in a heartbeat.