The crossword solution for the term AIR LINE is DUCT. DUCT is an acronym for 'Ductwork Uninsulated Conduit Technology' which is a type of air conditioning system used in many homes and businesses. It works by circulating air through a series of ducts, allowing for efficient cooling or heating of a space. DUCT systems are often used in conjunction with other air conditioning systems to provide a more efficient and cost-effective solution.