Can I take a 24" computer monitor on board?

I successfully managed to bring a 24" monitor home by air traveling, in 2011. This one:

But of course not in its original, unopened box. Right after I bought it, I was a bit worried: "how could I bring this bad boy home? I definitely don't want to check it. Even with the fragile tag, the panel is way, way too large and too delicate to travel together with other suitcases".

So on my last week before going home, I went to buy a backpack. I asked them for the largest size possible (well, but not too large, not the type you see hitchhiking travelers use). Luckily, the backpack could almost contain the monitor, and when I carry it on, looks not so bad. The monitor is flat and thin anyway.

I kept the monitor in its package for protection purpose till the boarding gate. With the box, the whole thing was so huge that it immediately raised the attention of the man at the check-in counter: "Sir, I notice you're not checking this, you're taking it as a carry on? You're not gonna make it man". But I persuaded him that it will be all right.

At the boarding gate, I threw away the box, attached some small patched to cover the corners and the panels, then I boarded without any problem.

The weight is not a problem. The gate attendants only care if your luggage is small/tidy/compact enough. For a 24" monitor, you cannot take it on-board in the original box, even if you're willing to pay. Its dimensions simply violate the aviation safety regulations.

EDIT: And one thing to add, that was 2011, where the airport security was not as strict as today's level (e.g. I never had to pulled out my laptop and my DSLR + set of lens prior to 2012). I put the whole thing (monitor + box) through the X-ray machine at the security gate without a problem, no one asked a question. But these days it will not get through that easily).

Personally I would say keep it in it's original box, packe it in a large suitcase surrounded by clothes and then check it in.

The original box will be designed to provide padding and support to the monitor in the right places. The suitcase full of clothes provides another layer of padding and makes it less obvious to potential theives what the item is (obviously security will know what it is whatever you do).

This August I traveled with a 27" monitor in checked luggage without any issues. The display was kept in the original box which we wrapped in plastic wrap to protect it and avoid the cardboard box getting damaged should it get wet which can happen if it rains while cargo is being unloaded or loaded.

The original box had Styrofoam at on top and bottom, plus some on the front and back of the monitor, so it was judge adequate and it was, even passing between planes as we did not have a direct flight.

You may want to read these two relevant questions and the top answers:

• Packing a cardbox box as checked luggage

• Can checked baggage on airplanes ever get wet?

The dimensions you provided are of the panel, not the box. Official product page:

Dimensions without stand (H x W x D):
Height: 13.80" (350.6 mm)
Width: 20.95" (532.2 mm)
Depth: 1.80" (45.7 mm)

I have written at length about carry on dimensions. Your panel without any packaging is already pushing it. 550 mm is the width usually allowed and the panel is 532.2 mm. The box and packing foam on each side can add 10-10mm and that's it. Also, the 350.6mm will be problematic as some airlines only allow 350mm in the first place but none allows more than 400mm but more typically just 380mm. So you are pushing it but without the box, you are probably good. Bubble wrap is good, handle it carefully. Ask the FA nicely to put it in the clothes cabinet instead of being jostled with the bags in the overhead bin. They just might. If you are in business class, they will be much more willing, that's for sure.

And there's the matter of the stand. That's also a problem: you can only have two pieces of luggage, if you attach the stand then a) it's really unwieldy to move around b) your monitor will be too high and the depth will be a problem too but if you don't then it becomes your personal item and you can't carry anything else really. It probably pushes the dimensions of personal item too but we would need to know the airline to know this. I would rather put the stand in the checked in luggage or mail it.