This industry comprises establishments primarily engaged in providing specialized services for air transportation (except air traffic control and other airport operations). Illustrative Examples: Aircraft maintenance and repair services (except factory conversions, overhauls, rebuilding) Aircraft testing services Cross-References. Establishments primarily engaged in-- ? Wholesaling fuel at airports--are classified in Industry 424720, Petroleum and Petroleum Products Merchant Wholesalers (except Bulk Stations and Terminals); ? Providing aircraft janitorial services--are classified in Industry 561720, Janitorial Services; ? Providing air traffic control services--are classified in U.S. Industry 488111, Air Traffic Control; ? Providing airport operations (except air traffic control)--are classified in U.S. Industry 488119, Other Airport Operations; ? Providing factory conversion, overhaul, and rebuilding of aircraft--are classified in Industry 33641, Aerospace Product and Parts Manufacturing; and ? Providing food services to airlines on a contractual arrangement--are classified in Industry 722310, Food Service Contractors.