http://www.legislation.gov.uk/eur/2012/601/article/55/2012-06-21Commission Regulation (EU) No 601/2012 of 21 June 2012 on the monitoring and reporting of greenhouse gas emissions pursuant to Directive 2003/87/EC of the European Parliament and of the Council (Text with EEA relevance) (repealed)Commission Regulation (EU) No 601/2012 (repealed)Commission Regulation (EU) No 601/2012 of 21 June 2012 on the monitoring and reporting of greenhouse gas emissions pursuant to Directive 2003/87/EC of the European Parliament and of the Council (Text with EEA relevance) (repealed)2020-12-11King's Printer of Acts of Parliamenthttps://webarchive.nationalarchives.gov.uk/eu-exit/https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32012R0601texttext/xmlen2012-06-21 CHAPTER IV <Strong>MONITORING OF EMISSIONS AND TONNE-KILOMETRE DATA FROM AVIATION</Strong> Sources of uncertainty Article 55 1 The aircraft operator shall identify sources of uncertainty and their associated levels of uncertainty. The aircraft operator shall consider that information when selecting the monitoring methodology pursuant to Article 52(2). 2 Where the aircraft operator determines fuel uplifts in accordance with point (a) of Article 52(3), it shall not be required to provide further proof of the associated uncertainty level. 3 Where on-board systems are used for measuring fuel uplift or fuel contained in tanks in accordance with point (b) of Article 52(3), the level of uncertainty associated with fuel measurements shall be supported by all of the following: a the aircraft manufacturer’s specifications determining uncertainty levels of on-board fuel measurement systems; b evidence of carrying out routine checks of the satisfactory operation of the fuel measurement systems. 4 Notwithstanding paragraphs 2 and 3, the aircraft operator may base uncertainties for all other components of the monitoring methodology on conservative expert judgement taking into account the estimated number of flights within the reporting period. 5 The aircraft operator shall regularly perform suitable control activities, including cross-checks between the fuel uplift quantity as provided by invoices and the fuel uplift quantity indicated by on-board measurement, and take corrective action if notable deviations are observed.