Transportation from Siena to Rome airport

Carol,
No, but you could take the train and pray for no problems. See http://www.trenitalia.com/

At the end of our trip to Florence, we took a train to Rome the day before, and stayed in a hotel near Termini. On the morning of the flight, we took the Leonardo Express from Termini to Fiumicino airport. This was very relaxing, and it gave us an opportunity to visit the Eternal City.

Once you get to Tiburtina, you can actually just jump on the FR1 Metropolitan train and it will take you all the way out to the FCO airport. It should take around 45 minutes - and at €8 it's a great deal. Although this may be a faster option than riding the metro and Leonardo Express , I agree with Douglas that I would NOT try and do this on the day of my flight. The first SENA bus leaves about 06:00 from Siena and arrives at Tiburtina at 09:25. You could walk over and catch the next FR1, which departs every 15 minutes. You might get lucky and catch the 09:47 train, but it does not arrive at FCO until 10:34 (the next one arrives at 10:47). Then you have to walk from the FCO Train Station and find your check-in counter. Since you're check-in counter closes probably 40-45 minutes prior to your flight, you're basically working with a 25-30 minute window. For me, given the "timeliness" of trains and buses in Italy... that's just too close. So I'd come in the night before.

The Sena bus goes direct to Tiburturna Station in Rome. From there you can take the metro to Termini and catch the Leo express to the airport. It's a 3 hour bus ride so unless there is a very early departure, you will not be able to catch a noon flight. The train is no faster and requires a transfer.