F$_{N}$ = Fuel allocated to the international flight under consideration (i.e. flight $_{N}$) using the Fuel  Allocation Block Hour method (in tonnes);  AFBR$_{AO,AT}$ = Average fuel burn ratios for aeroplane operator (AO) and aeroplane type (AT) (in  tonnes per hour)( a )( b ); and  BH$_{AO,AT,N}$ = Block hour for the international flight under consideration (i.e. flight $_{N}$) for aeroplane  operator (AO) and aeroplane type (AT) (in hours).  (6) A verification body must cross-check whether the emissions reported are reasonable in  comparison to other fuel related data of the aeroplane operator.  Article 70(3)  1.  The procedures specified in this Schedule are concerned with the estimation of CO$_{2}$ emissions  by an aeroplane operator for the purposes of monitoring CO$_{2}$ emissions and filling data gaps. The  methods and tools proposed are representative of most accurate established practices.  2. —(1) The aeroplane operator must use the CERT according to the eligibility criteria as  described in article 22 of this Order and upon approval by the Regulator.  (2) The aeroplane operator must use either—  to enter the necessary information into the CERT.  (3) The aeroplane operator approved to use the Block Time input method—  50 ( e )  The destination aerodrome designators are contained in Doc 7910 – Location Indicators. The CERT will automatically  compute Great Circle Distance based on the origin aerodrome and destination aerodrome.  ( d ) The origin aerodrome designators are contained in Doc 7910 – Location Indicators which is available from the ICAO  website at www.icao.int. For a hard copy contact the ICAO E-Commerce and Publications Sales Unit at International Civil  Aviation Organisation (ICAO), 999 Robert-Bourassa Boulevard, Montreal, Quebec H3C 5H7, Canada (telephone +1 514- 954-8219 and e-mail sales@icao.int). The CERT will automatically compute Great Circle Distance based on the origin  aerodrome and destination aerodrome.  ( c )  The ICAO aircraft type - model designators are contained in Doc 8643 — Aircraft Type Designators which is available  from the ICAO website at www.icao.int. For a hard copy contact the ICAO E-Commerce and Publications Sales Unit at  International Civil Aviation Organisation (ICAO), 999 Robert-Bourassa Boulevard, Montreal, Quebec H3C 5H7, Canada  (telephone +1 514-954-8219 and e-mail sales@icao.int).  ( b ) The Verification Report of the external verification body includes an assessment of the aeroplane operator specific average  fuel burn ratio per ICAO aircraft type designator used.  ( a ) AFBR based on all flights for a reporting year and rounded to at least three decimal places.  (i) date, and  (b) may collect the following data and, if collected, must enter it into the CERT to estimate  its CO$_{2}$ emissions during the compliance year—  (v) number of flights,  (iv) Block Time (in hours), and  (iii) destination aerodrome ICAO Designator( e ),  (ii) origin aerodrome ICAO Designator( d ),  (i) ICAO aircraft type - model designator( c ),  (a) must collect the following data and must enter it into the CERT to estimate its CO$_{2}$  emissions during the compliance year—  (b) the Great Circle Distance input method,  (a) the Block Time input method, or  SCHEDULE 3  CO$_{2}$ emissions estimation and reporting methods and tools  Introduction to the ICAO CORSIA CO$_{2}$ Estimation and Reporting Tool (CERT)  Use of the CERT for complying with monitoring and reporting requirements 