Can I check a cooler as luggage on a flight?

Yes, but only if it fits the airline’s size and weight limits (usually 62 linear inches total for checked bags). The real headache is what’s inside: no large amounts of liquids or semi-liquids (like soup or marinated meats) unless frozen solid—but melting is a problem. Dry ice is allowed for perishables, but most airlines cap it at 2 kg (4.4 lbs) per bag and require it to be marked.