(6) If the aeroplane operator’s annual CO$_{2}$ emissions from international flights increases above  the threshold of 500,000 tonnes in 2019, the Regulator may permit the aeroplane operator to  continue to apply the monitoring method chosen in accordance with paragraph (5) for this period.  2021-2035 period  (7) An aeroplane operator, with annual CO$_{2}$ emissions from international flights between State  Pairs defined in the ICAO document entitled “CORSIA States for Chapter 3 State Pairs”( a ) of  greater than or equal to 50,000 tonnes, must use a Fuel Use Monitoring Method as described in  Schedule 2 for these flights. For other international flights, the aeroplane operator must use either  a Fuel Use Monitoring Method, as described in Schedule 2, or the CERT, as described in Schedule  3.  (8) An aeroplane operator, with annual CO$_{2}$ emissions from international flights between State  Pairs defined in the ICAO document entitled “CORSIA States for Chapter 3 State Pairs” of less  than 50,000 tonnes, must use either a Fuel Use Monitoring Method or the CERT as described in  Schedules 2 and 3, respectively.  (9) If an aeroplane operator’s annual CO$_{2}$ emissions from international flights between State  Pairs defined in the ICAO document entitled “CORSIA States for Chapter 3 State Pairs”, increases  above the threshold of 50,000 tonnes in a given year (y), and also in year (y+1)( b ), the aeroplane  operator must—  (10) If an aeroplane operator’s annual CO$_{2}$ emissions from international flights between State  Pairs defined in the ICAO document entitled “CORSIA States for Chapter 3 State Pairs” decreases  below the threshold of 50,000 tonnes in a given year (y), and also in year (y + 1), the aeroplane  operator may change monitoring method on 1st January of year (y + 3).  (11) Where an aeroplane operator chooses to change its monitoring method under paragraph  (10)( e ), it must submit an updated Emissions Monitoring Plan by 30th September of year (y + 2).  (12) Where the aeroplane operator has, prior to this Order coming into force, accumulated any  fuel use during 2021 pursuant to article 3 of Commission Implementing Regulation (EU)  2019/1603 in conjunction with article 24 of the UK ETS Order, that fuel use data must be used for  the purpose of this Order  23. —(1) An aeroplane operator must submit an Emissions Monitoring Plan to the Regulator for  approval by the Regulator. The Emissions Monitoring Plan must contain the information set out in  Schedule 4.  (2) Where an aeroplane operator has, prior to this Order coming into force, established an  approved Emissions Monitoring Plan pursuant to article 3 of Commission Implementing  Regulation (EU) 2019/1603( f ), a Regulator must, before 30th June 2021, approve and issue an  Emissions Monitoring Plan to that aeroplane operator in the same terms, subject to any variation  required to comply with this Order.  (3) A new entrant aeroplane operator must submit an Emissions Monitoring Plan to the  Regulator for approval and issue within 3 months of falling within the scope of applicability set  ( a ) “CORSIA States for Chapter 3 State Pairs” 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 ) “(y + 1)” refers to the year following the increase above the threshold.  ( c )  “(y + 2)” refers to the second year following the increase above the threshold.  ( d ) “(y + 3)” refers to the third year following the increase above the threshold.  ( e )  See Volume IV of Annex 16 to the Chicago Convention, Attachment B, Figure B-3, for a process flowchart on the  eligibility of Fuel Use Monitoring Methods during the 2021-2035 Compliance Phases.  ( f )  OJ L 250, 30.9.2019, p.10.  15 Emissions Monitoring Plan  (b) change to a Fuel Use Monitoring Method, as set out in Schedule 2, on 1st January of year  (y + 3)( d ).  (a) submit an updated Emissions Monitoring Plan by 30th September of year (y + 2)( c ), and 