Airwise.com
Telephone numbers of carriers at Fiumicino Airport.
http://www.airwise.com/airports/europe/FCO/FCOarl.html

Alitalia
Italy's national airline.
http://www.alitalia.com/

Enjoy Rome
Addresses and telephone numbers of airline offices in Rome itself.
http://www.enjoyrome.com/tourist/cityguide/airline.offices.html

Roman Homes
The details of airline offices in the both the city centre and Fiumicino.
http://www.romanhomes.com/your_roman_vacation/airline.htm