3. Air navigation service providers shall, in their internal accounting, keep separate accounts for each air navigation service as they would be required to do if these services were carried out by separate undertakings with a view to avoiding discrimination, cross-subsidisation and distortion of competition. An air navigation service provider shall also keep separate accounts for each activity where:
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(a)
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it provides air navigation services procured in accordance with Article 11(1) and 11(2) and air navigation services not covered by that provision;
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(b)
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it provides air navigation services and carries out other activities, of whatever kind, including CIS;
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(c)
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it provides air navigation services in the Union and in third countries.
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The determined and actual costs deriving from air navigation services shall be broken down into costs categories in accordance with Article 30(6) and they shall be made publicly available, without prejudice to Article 52(3).