Fiumicino Airport Passport Control

I wouldn't risk it. That is very tight, especially with checked baggage. I carry on but have heard that baggage claim at FCO is super slow. I'd just wait until the direct 3 - much less hassle. Really, that's only 4 hours, much of which will be taken up with deplaning, passport and baggage. There won't be much time to kill, really.

Is there any way you can travel using just carry-on? That will speed you up immeasurably. You might even consider shipping something ahead of you so you can avoid checking (and waiting for) a bag.

I never book any train in advance upon landing. Too many variables can cause delays in air travel. I always purchase tickets at the Fiumicino station whenever I get to it. There are so many trains going from Rome to Venice (1+ per hour) that there is virtually zero chance of a sold out train, especially later in the morning or early afternoon, and in October.
But if you already purchased a discounted ticket (super economy or economy fare) it's too late now. Those discounted tickets are non refundable and non changeable. Only full 'base' fare can be changed or refunded.

Since you already have the ticket, hope for the best. Worst case, you will have to buy another train ticket at the airport.

If you brush up on your Italian and come prepared to show your train ticket to the guards (pointing out the train departure time), you might be lucky enough to have them send you to the front of the line. You could also try explaining your concern to a gate agent for your airline as soon as you step off the plane (the personnel who stand there to direct people on connecting flights). They could both be totally unhelpful, but it might be worth a try.

In the unfortunate event that your flight is already late to where there's no realistic chance of making it to the train station, just grin & bear it.

Passing the time at Fiumicino until 3 PM shouldn't be a problem, just take your time availing yourselves of the restrooms, then sit down with a coffee and a newspaper, and it will be time to go to the train platform before you know it.

When I check the trenitalia website, I don't see a train departing at 12:30, only at 12:57, connecting with the Frecciarossa train (#9430) at Roma Tiburtina at 14:00 (15 minute transfer time). Is this the ticket you have?

If you travel with carry-on only, & if your plane is on time & if the line for passport control is short...

You might just make it...

Is the ticket you bought a SuperEconomy ticket? If it is, you may be out of luck as far as the ticket price is concerned. If it is an Economy ticket, you can change it one time before departure, same departure station and routing to same destination station, by paying the difference between the original price you paid and the current price. If it is a Base fare, then its a free change (you already paid top fare).

Since the portion from the airport to Roma Tiburtina is a Regionale and you bought on line, it should come prevalidated for 4 hours from the train time on the ticket, so it will remain valid for another 3 hours or so from 12:57 (if that is the time on the ticket). Therefore, if you do have to buy a new ticket to Venice, you will just have to pay for the portion from Roma Tiburtina to Venice. That will save you a whole 16 EUR. Whoopie.

Of course if your inbound flight is seriously delayed, that ticket will time out as well.

Since you will be going to Venice, only take carry-on luggage. Venice is not the place to have over-sized or heavy luggage. And, now you'll have a better chance catching that train.

definitely check your train ticket but I think you are fine.. We missed a train (which meant we would miss the next one as well...)-talked to a ticketing agent at the station were told the tickets were good, just take the next train-- the agent on the train who checked our tickets had no problems... - here's what our economy tickets state: 2. Tickets are
2.1. nominative, personal and non-transferable
2.2. pre-validated and allow the journey to begin by 4 hrs 0 minutes from the date/hour shown on this receipt.
3. The travel document must be shown (on paper or electronic equipment able to permit the correct visualization of the file in pdf.) jointly with a valid identity document upon every
request of the Inspectors. By failing to show even only one of the two, the passenger is considered devoid of the ticket and regulated according to current regulations. 4. It is not possible to bring the departure forward
5. It is not permitted to change the ticket

There is an 11:27 train that connects to service at Tiburtina at 12:30 with a 15 minute layover, but it involves additionally changing trains at Bologne and Mestre, so 4 trains total.

If you mean Tiburtina Station when you say "Departs at 12:30," then you haven't got any reasonable chance of making to from a landing plane to the FCO rail station in less than 30 minutes. As this is a Sunday you could try to cab it to Tiburtina to catch the train there.
Not clear what your situation really is, I checked Italo and nothing there lines up with a 12:30 FCO train departure, either.

Tom_MN,

When the OP posted this:

We purchased train tickets from Fiumicino to Roma Tiburtina (Departs at 12:30), then changing trains heading to Venice (we will have 15 minutes to change trains).

I presumed he meant the train would be departing at 12:30 from the airport.

I guess we won't know what the OP meant until he/she posts again...

Thank you for all of the replies. Looks like I typed my times incorrectly in the original post. We actually land at 10:30, with our train scheduled to leave the airport at 11:57 am, arriving at Roma Tiburtina at 12:45, then departing for Venice at 1:00 pm. We did purchase Super Economy tickets, so refunds don't look like they will be in the picture. I'm not going to get my hopes up that we will make the train, but you never know. If we only slightly miss it, I think we will use our prevalidated regionale ticket to get to Roma Tiburtina and then take the next train to Venice. If we don't finish up with passport control until later, I'm thinking we will stick around until the direct train from the airport. Thank you again for the information, I appreciate it!

Btriffo,

That's still going to be really tight if you're arriving from North America. You'll be on a big plane and if you're seated towards the rear, it could take 15 minutes just to get off the plane. Then, you're bags will need to be x-rayed before being released at baggage claim. THEN, you need to go through passport control and customs.

I would downsize your luggage and take carry-on only. This way, you can bypass the baggage claim and go straight for passport control. And, as another person said, Venice is NOT the place for large suitcases.

Come to mention it, neither is the train. A carry-on sized bag will fit on the shelf above your seat but anything wider than 14 or 15 inches will not. That means your bag will need to be placed in the luggage spaces at either end of the train (space permitting). Do you really want to try to keep an eye on your bags, from afar, for the entire trip to Venice?

Concerning the train tickets, generally the pre-purchased fast train tickets are not transferable. If you miss the train, you have to purchase another ticket (unless it's the fault of the railway). The previous commenter may have had tickets on a Regional train which ARE transferable. Bottom line, if you ticket lists a train, carriage and seat number, it's valid ONLY on that train. If it doesn't list a train, carriage and seat number, it's for a regional train and MUST be validated before getting on a train.

it's for a regional train and MUST be validated before getting on a train.

Regionale tickets purchased online with a connecting Freccia or IC train come prevalidated with a 4 hour use window.

I should clarify, after Venice we will also be going to Florence and back to Rome. We will be there for two weeks. We won't be bringing any rolling luggage, just our backpacking backpacks.

As was said, if you can get these down to meet your airline's size and weight limits for carry-on luggage, you will be ahead of the game.