# Commission Implementing Regulation (EU) No 923/2012 of 26 September 2012 laying down the common rules of the air and operational provisions regarding services and procedures in air navigation and amending Implementing Regulation (EU) No 1035/2011 and Regulations (EC) No 1265/2007, (EC) No 1794/2006, (EC) No 730/2006, (EC) No 1033/2006 and (EU) No 255/2010 (Text with EEA relevance), Division (b): Inadvertent changes. In the event that a controlled flight inadvertently deviates from its current flight plan, the following action shall be taken:

Extent: E+W+S+N.I.

(1)Deviation from track: if the aircraft is off track, action shall be taken forthwith to adjust the heading of the aircraft to regain track as soon as practicable.
(2)Variation in true airspeed: if the average true airspeed at cruising level between reporting points varies or is expected to vary by plus or minus 5 per cent of the true airspeed, from that given in the flight plan, the appropriate air traffic services unit shall be so informed.
(3)Change in time estimate: if the time estimate for the next applicable reporting point, flight information region boundary or destination aerodrome, whichever comes first, is found to be in error in excess of 2 minutes from that notified to ATS or such other period of time as prescribed by the competent authority, a revised estimated time shall be notified as soon as possible to the appropriate ATS unit.
(4)Additionally, when an ADS-C agreement is in place, the air traffic services unit shall be informed automatically via data link whenever changes occur beyond the threshold values stipulated by the ADS-C event contract.

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Source: https://www.legislation.gov.uk/eur/2012/923/annex/section/8/division/SERA.8020/division/b (the official version)
Page: https://openlegislation.uk/eu-regulation-2012-923/annex/section-8/division-SERA.8020/division-b
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.