The strike, which will last from 1pm to 5pm, has already prompted Alitalia to cancel more than 100 domestic and international flights (find a full list here).
Most of those affected are flights between Rome or Milan and other cities within Europe, with long-haul flights expected to escape the disruption.
Alitalia says it hopes to rebook passengers on alternative flights the same day, but it expects at least 20 percent of travellers to have to reschedule. Passengers can rebook at no extra cost, while those whose flights are cancelled or delayed by more than five hours are entitled to a full refund.
Low-cost airline Vueling has also cancelled several European flights and warns that other may be delayed (more details here).
Both easyJet and Ryanair said that they were expecting disruption, and said that they would contact passengers directly to warn them if their flight was affected.
Air traffic control unions called the four-hour strike to protest what they say are continual operational problems.
If you're travelling today, make sure you check for updates from your airline before setting off.
For more information:
- Alitalia: check the website, or call toll-free number 800 65 00 55 (within Italy) or +39 06 65 649 (from overseas).
- easyJet: go to easyJet.com/XXXX (your flight number) to track the status of your flight.
- Ryanair: use the airline's online flight tracker.
- Vueling: find your flight status online or call +34 931 224 900 (international) or +39 (0) 694 802 764 (within Italy) for assistance.