# The Air Navigation Order 2016, Paragraph 1


A non-Part-21 aircraft registered in the United Kingdom may fly for a purpose set out in paragraph 2 or 3 subject to the conditions contained in paragraphs 4 to 7 when—
(a) it does not have a certificate of airworthiness duly issued or rendered valid under the law of the United Kingdom;
(b) the certificate of airworthiness issued under article 38 for the aircraft has ceased to be in force by virtue of any of the matters specified in article 39;
(c) it has previously had a permit to fly but that permit has ceased to be in force by virtue of any of the matters specified in article 41; or
(d) is of a design which has previously been approved by the CAA, or by an organisation approved for that purpose by the CAA, as being compliant with a standard accepted by the CAA as appropriate for the issue of a national permit to fly.

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Source: https://www.legislation.gov.uk/uksi/2016/765/schedule/3/part/1/chapter/1/paragraph/1 (the official version)
Page: https://openlegislation.uk/air-navigation-order-2016/schedule-3/part-1/chapter-1/paragraph-1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.