1. Before receiving approval or information in accordance with Article 15(2), the operator or aircraft operator may carry out monitoring and reporting using the modified monitoring plan where it can reasonably assume that the proposed modifications are not significant, or where monitoring in accordance with the original monitoring plan would lead to incomplete emission data.

In case of doubt, the operator or aircraft operator shall use in parallel both the modified and the original monitoring plan to carry out all monitoring and reporting in accordance with both plans, and it shall keep records of both monitoring results.

2. Upon receipt of approval or information in accordance with Article 15(2), the operator or aircraft operator shall only use the data relating to the modified monitoring plan and carry out all monitoring and reporting using only the modified monitoring plan from the date from which that version of the monitoring plan is applicable.

3. The operator or aircraft operator shall keep records of all modifications of the monitoring plan. Each record shall contain:

(a) a transparent description of the modification;

(b) a justification for the modification;

(c) the date of notification of the modification to the competent authority pursuant to Article 15(1);