Is this bag too big for hand luggage?

Any bag or item that you take with you into the penger compartment must be able to fit in the overhead compartment or under the seat. Both spaces are about 9"x9"x12" give or take. If the bag is larger than that it will have to be checked. You can take only 2 carry-on bags with you. There is one other way but most people won't want to do it. This way is to buy two seats together and in this way your luggage can take the place of a person. That is what I did on my return home trip because of extra junk I purchased.