The Swedish Armed Forces tend to ask themselves if it is sufficiently multinational interoperablefor participation in international operations. An equally valid question today should be whether theSwedish Armed Forces are sufficiently nationally / internally interoperable, between their branchesof service, to be able to conduct independent operations based on the joint warfare theory.The lack of ability to joint warfare in the armed forces in general and the Swedish Armed Forcesspecially constitutes the essay´s fundamental problem. By using Codners and Sjöbloms custominteroperability theory, the Swedish Armed Forces documents were analyzed to highlight anyweaknesses related to joint warfare and national interoperability between Ground and Air Forces.The survey shows weaknesses linked to the custom theory and Swedish Armed Forces governingdocuments. The ability of a national interoperability is limited between Ground and Air Forcestoday, mostly because of weaknesses in the Swedish Armed Forces strategic concept which doesnot describe the importance of joint warfare at all levels sufficiently. This leads to deficienciesreflected in doctrines, regulations, technology, techniques and exercises. Lack of common documents,techniques, methods and exercises in turn affects armed services understanding of theirdifferent backgrounds and unique perspectives. The result will therefore be low national interoperabilityamong the armed services.