Size for personal carry on's

This is a good question. I have this bag. It can be used as an underseat bag. The space under seats vary. If this bag is fully packed, it can be hard to put under the seat on some airlines. It can count as a big "purse." So, you can do a carry on suitcase and bring this as an underseat bag. Personally, I am not a fan of this bag for flying. I like it better for car trips. I carried it over my shoulder through a couple of airports and found it "boxy" bulky and uncomfortable to lug around. I also carried it around a convention for a couple of days and again, found it uncomfortable to carry. I only use it for car trips now. You would do better with a different underseat bag. Some ideas are the RS veloce bag, small backpack, tote bag with zipper, travel purse, medium or large packing cube with a strap handle. Check out ebags.com Classic ebags cubes or Eagle Creek products. There are many brands of
good products for an underseat bag. Even a simple cinch bag.

I just wanted to note that Delta normally has good underseat space. So, you can stack the EuroFlight bag on top of your suitcase and carry both on. Alitalia is a different story. I would have had problems. I prefer something lighter weight, smaller, and more squishable for underseats now. I don't like carrying the EuroFlight bag at all over my shoulder whether crossbody or same side. It makes me too lop-sided and uncomfortable.

I've now use the Euro Flight Bag on a bunch of planes, of various sizes, both domestic and international. Most recently, I took it as my "personal item" on Delta from JFK to Zurich. I've never had trouble fitting it under the seat. I take it in addition to a larger "carry on" bag.

It is definitely acceptable as a personal item, unless you're on one of the budget European airlines. In the Liverpool airport, I encountered a bunch of sizer boxes for various airlines such as Ryanair, EasyJet and Wizz Air. My fully packed Euro Flight Bag was too big to be a "personal item" on all three of them, although since it's totally squishable, it would have worked if it hadn't been so full. It could also have been a "carry on" with these airlines, meaning I would have had to check the bigger bag.

So, short version - for Delta, it's fine.

Delta has incredibly lax enforcement of carry on. You will be fine

Thank you for the information given. Much appreciated!!
Good to know about Alitalia also. Our return flight from Italy to the states is with them, but we plan to check baggage on the way back home anyway.