Carry On Limitations for International Travel

To me it seems the best source of accurate info would be the airline

This doesn't exactly answer your question, but.... some five weeks ago, I flew on Delta to FCO then flew Alitalia to Catania a few hours later. (The tickets were booked separately.) I carried on my Delta-carryon-size 2-wheeled bag onto the Delta flight, then just strolled right onto the Alitalia flight with it and no one stopped me. I was prepared for an Alitalia gate agent to challenge me, and to perhaps have to pay a fee at the gate to gate-check it, but mine was not the largest carryon there, and no one bothered to challenge me. When boarding the Alitalia flight, I had to carry the bag up steps into the plane, and so carried my bag up those stairs. It then fit in their overhead compartment. This doesn't mean that you would have the same experience, but this was mine.

Same experience as jmauldinuu. However, you never know what can happen. Note that if you're ticketed all the way through on Delta Premium Economy, Alitalia does not call their's Premium Economy, but you are still entitled to priority boarding. Look for the words "priority" or something similar on your boarding pass, and then see the separate line at the gate for first class, and whatever they call their priority group. Its not clear otherwise. Sorry I can't remember the keyword, but it lets you board before the rest of the cabin as you do with Delta PE.

A little confusion here. At one point you’re flying to Catania and then checking your bag to Palermo? Hmmm... Sometimes Alitalia doesn’t monitor any bags but those obviously too large for carryon and I’ve seen, and been a victim of, just the opposite where they’ve had all pax put their bags into a sizer and then weigh them. The only time i ever had to pay for a checked bag on Alitalia was flying Catania to Naples on one of their low cost subsidiary airlines (operated by Darwin Airline) at their lowest fare.

I would be cautious. I have found Alitalia to be rather capricious. I unfortunately had the exact opposite experience than @stan and @jmauldinuu. The Alitalia gate agent made us check our bags even though they were carry on size and the aircraft was a jet with plenty of overhead bin space.

Thanks everyone for your responses. Your answers are helpful in that it can be different with different gate agents. So, we'll just see what happens.

By the way, Philip, I didn't mean to be confusing...I accidentally said Palermo the second time because we are flying back from there and I had it on my mind. :)

remembering now that Delta calls their premium economy class "comfort plus" I believe. Thats what we had and entitled us to priority boarding on Alitalia flight.

I have no problem with my carry on with Delta, but I did when I had to take Alitalia for the last leg(booked on 1 ticket). They made me gate check it even though there was plenty of room on plane as earlier poster said. I was told that I could pick it up on the tarmac when we arrive, but that did not happen. I had to wait with everyone else for the checked luggage. I was wonderiing why they promised that as I didn't think that anyone was going to be separating out the carry ons from the larger luggage! So it is a toss up as to what will happen.

Thank you, Diane. Our flights are booked on one ticket as well so in all likelihood we will experience the same thing you did. Bags checked at the gate come off the plane first so they can easily be given to the owner at the plane. It's not good that they made you pick them up at baggage claim. That's just more tossing around and possible damage to your bag. I guess that's just all part of being a world traveler.:)