What is the best way to get to the airport on a Monday morning from a hotel near the Pantheon? Shuttle? Taxi? Train? Need to arrive by 9 am.
Are you traveling alone or with others?
You need to define best because some think best is cheapest. The best way will be a taxi - door to door - fixed rate of 48 Euro. A shared shuttle will work well also. The hotel will arrange that. You are near the Pantheon so you have the hassle of getting to Termini if you want to take the train.
I would take a city taxi for the flat rate of 48e. I wouldn't be so sure that your hotel would arrange a shared shuttle. Many hotels will only arrange transfers with a driver they have a relationship with. Rick lists several shuttle services is his book, arrange one on your own.
The train is running at that time of day, but I'm guessing that your hotel is not very close to a metro station to take you to the train. Reserve ahead for either a taxi or a shuttle. www.airportshuttle.it is a little cheaper than a taxi, but since the taxi rate is fixed, it's easy to compare the relative price and convenience for yourself or your party.
Shuttles are a lot cheaper than Taxi's.. do a search for Rome airport shutte . We used one and glad we did. Its easy to do yourself online and you can even pay for them online. Ours picked us up in front of our hotel. Save your money and use a shuttle
We were in Rome 2 weeks ago and used the shuttle service recommended in Rick Steves' book called Rome airport shuttle--I think it cost us around 35 euros for 2 of us. They were very professional & called us when they were going to be 10 min late. It was worth the piece of mind.