The International Air Transport Association (IATA) has estimated that the baseline would be about 30 per cent more strict than originally anticipated before the COVID-19 crisis, meaning that the airlines would need to purchase 30 per cent more carbon credits to offset their emissions. IATA announced early that the International Civil Aviation Organization (ICAO) should change the baseline from an average of 2019 and 2020 emissions and instead use a 2019-only baseline. The European Commission recommended European states to support the proposal by the airline industry to change the CORSIA baseline to take into account the expected sharp decline in carbon emissions in 2020 due to the COVID-19 outbreak. 

In a letter to ICAO Council sent May 25, environmental NGOs Environmental Defense Fund (EDF), WWF and Carbon Market Watch, Gold Standard, Climate Action Reserve, atmosfair, and other market stakeholders, urged the Council not to modify the baseline calculation to only be based on 2019 emissions. According to their estimates, a 2019 baseline would eliminate all offsetting requirements for the duration of the pilot phase and potentially several years after, resulting in a postponement of the start of CORSIA by three to five years regardless of post-COVID-19 crisis recovery scenarios.