Messenger bags

What airline? I think that size would be acceptable to the domestic airlines as long as it will fit under the seat.

Usually the rules will say something like "personal item, such as a purse, small backpack, computer bag, etc." In my experience, if the airline allows a personal item, they are pretty loose in defining it as long as it fits under the seat.

lynn, If you're planning to use any of the budget airlines in Europe, they usually allow only one carry-on item. That doesn't mean "one plus a personal item such as a Purse or Laptop case", it means ONE ONLY of the approved size (and they likely will check the size, perhaps more than once). I suspect you'll either have to check your carry-on or find some way to place your Purse inside so that you just have "one" item. If you have to check one bag at the boarding gate, there's usually an exorbitant charge associated with that. Happy travels!

Lynn, The best thing to do is check the website of the airline on which you're traveling. We like to take Virgin Atlantic and they are pretty generous in the number of items you can carry on. However they note that a purse must be used "as you would normally use it (in other words, not just being used to contain items that would otherwise be regarded as baggage).", so you can't use it as an extra carry-on bag. Plus, as noted by others, you'll need to be able to stow it under the seat when they want everything put away for take-off and landing.

Lynn: I just want to emphasize the importance of checking the rules for the airline(s) you are flying. I'm finding more variation than ever before, and as Ken said, they are checking more carefully than before so they can charge money for "violations" (if you wanted to carry on a bag that doesn't meet their carry-on regulations, they will charge you to check it). Be PARTICULARLY careful with budget airlines, and with flights within Europe (budget carrier or not). Trans-Atlantic flights usually are more generous, but that's changing too (my upcoming Air Berlin flight from New York to Berlin only allows a carry-on to weigh 6 kg or less, which is the lowest carry-on limit I've encountered - to date). My guess it that if your airline allows a personal item in addition to your carry-on, a messenger bag would be allowed. But that's all it is - a guess. Double check to be sure.