The global carbon offsetting system created by the International Civil Aviation Organization (ICAO) is the first of its kind for the aviation industry. It is expected to slow down the increase in emissions from commercial flights, with the cost to the industry being less than 2% of revenues. While individual governments still need to take action to enforce the limits set by the agreement, the system will be voluntary from 2021 to 2026 and mandatory from 2027 for states with larger aviation industries. Airlines will need to purchase carbon credits from specific environmental projects worldwide to counterbalance the growth in emissions. According to Olumuyiwa Benard Aliu, president of ICAO's governing council, the agreement is a result of compromises and consensus. Aliu stated that the plan would not be derailed by objections from a small number of countries. He mentioned that 65 countries, accounting for over 80 percent of aviation activity, had exceeded the agency's expectations by participating in the voluntary first phases, and that participation would continue to increase. The tensions primarily revolved around developed nations, which have historically been responsible for the majority of greenhouse gas emissions, and emerging and developing countries concerned about potential cost implications hindering growth. Russia and India have declined to participate in the voluntary phases, citing an unfair burden on emerging nations. Conversely, China has announced its intention to join the voluntary phase. Brazil, which previously had concerns, has now expressed support for the deal without confirming participation in the initial stages. According to ICAO data, the agreement is estimated to cost airlines between $1.5 billion and $6.2 billion in 2025, depending on carbon prices, and no more than 1.8 percent of industry revenues by 2035. Airline profit margins have been narrow, averaging 4 percent over the past decade, as reported by the International Air Transport Association. Despite the additional cost, IATA believes the deal is more cost-effective than various national and regional climate agreements. Paul Steele, an IATA vice president, stated that while the industry dislikes additional expenses, they view this as a manageable cost. The US Department of State, after advocating for a deal, stated that it sets the industry on a path towards sustainable, carbon-neutral growth. However, environmentalists argued that due to the voluntary phase and exceptions for smaller markets, the scheme would not achieve its objectives. The International Council on Clean Transportation predicted that the agreement would only require airlines to offset around three-quarters of growth post-2021, which is a quarter of total international traffic. Some critics also disapproved of the deal's reliance on offsets, with Transport and Environment director Bill Hemmings stating that flying is the quickest and cheapest way to harm the planet, and this agreement will not decrease the demand for jet fuel. Discussions will now focus on the technical specifics of the agreement, particularly the types of offset credits that will be deemed acceptable. The deal was approved by a Montreal assembly of ICAO's 191 member states and will impact international passenger and cargo flights, as well as business jets producing over 10,000 tonnes of emissions annually. Previous talks almost led to a trade dispute prior to the 2013 ICAO assembly when the European Union, dissatisfied with slow progress, mandated foreign airlines to purchase credits under its program, prompting objections from China and other nations citing sovereignty concerns. The agreement was reached the day after the implementation of the Paris accord to combat climate change. Aviation was not included in the agreement, despite the fact that the industry is responsible for approximately 2% of carbon dioxide emissions, which is more than what some industrialized nations produce. With the expectation of passenger numbers doubling to 7 billion by 2034, it is essential to reduce aircraft pollution in order to meet the temperature targets set in Paris, according to Lou Leonard, a vice president at the World Wildlife Fund.