Anything you carry onto the plane is counted as part of your carry-on. Whether you are allowed a special cooler bag with all kinds of food depends on security and sometimes the airline. Cooler bags as such are not a problem, I used one in the past but only because it was a nice shape.

Yes, a cooler bag counts toward your baggage allowance and is generally treated as either a "personal item" or a "carry-on" depending on its dimensions. In 2026, most major airlines like American and Delta allow soft-sided cooler bags as long as they fit under the seat (typically 18 x 14 x 8 inches) or in the overhead bin. The most critical restriction involves the ice packs inside: TSA rules state that ice or gel packs must be frozen solid at the time of security screening. If they are even slightly melted or slushy, they are treated as liquids and must comply with the 3-1-1 rule (3.4oz or less). Exceptions are made for medically necessary items, breast milk, or baby food, which can be carried in larger quantities but must be declared for separate screening. Always use a leak-proof bag to prevent messes that could lead to your bag being removed from the cabin.