- Australia
- Ansett Airlines
- Qantas
- Trans Australia Airlines
- Austria
- Bolivia
- Brazil
- Canada
- Air Spray (aerial firefighting)
- Buffalo Airways
- Conair Group (aerial firefighting)
- Northwest Territorial Airways
- Nordair
- Colombia
- Republic of the Congo
- Costa Rica
- Ecuador
- El Salvador
- TACA International Airlines
- Guyana
- Honduras
- Hong Kong
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- Indonesia
- Garuda Indonesia Airlines
- Mandala Airlines
- Ireland
- Laos
- Mexico
- Banco de México (corporate aircraft)
- Netherlands
- Netherlands Antilles
- Norway
- New Zealand
- Panama
- Paraguay
- Peru
- Líneas Aéreas Nacionales SA
- Philippines
- São Tomé and Príncipe
- Sweden
- Taiwan
- Winner Airways (one 188A leased from Eastern Air Lines for only 2 months in 1970)
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- United Kingdom
- Air Bridge Carriers
- Atlantic Airlines
- Channel Express
- United States
- Air California
- Air Florida
- Air Holiday
- American Airlines
- Braniff Airways
- Denver Ports of Call
- Eastern Air Lines
- Evergreen International Airlines
- Federal Aviation Administration
- Fairbanks Air Service
- Great Northern Airlines
- Hawaiian Airlines
- Intermountain Airlines
- Johnson International Airlines
- McCulloch International Airlines
- NASA
- National Airlines
- National Center for Atmospheric Research
- Northwest Orient
- Overseas National Airways
- Pacific Southwest Airlines
- Reeve Aleutian Airways
- Saturn Airways
- Shillelagh Travel Club
- Southeast Airlines
- Trans International Airlines, later became Transamerica Airlines
- TPI International Airways
- Western Air Lines
- Zantop International Airlines
- Zaire
- Karibu Airways
- Trans Service Airlift
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