The United Nations has agreed to cut airline emissions after 2,000 delegates met at the International Aviation Organization in Montreal this week. Under the deal, 191 nations agreed to curb or offset emissions from passenger and cargo flights that produce more than 1,000 tons of greenhouse gas each year. 

The deal regulates carbon emissions from planes for the first time ever by setting airline emissions from the year 2020 as the upper limit of what carriers are allowed to emit, McClatchy reported Thursday. Airlines that exceed the limit will have to offset emissions by funding forested areas and other carbon reducing activities. The agreement will cost airlines less than 2 percent of the industry's total revenue, according to Reuters.

It will only become mandatory in 2027 for the world's largest emitters. That one large global agreement will cost less for airlines than a multitude national and regional regulations combined is likely one of the main reasons for its ratification.

The deal aims to reduce the increasing climate impact of airplane travel. The average Boeing 747 burns approximately 36,000 gallons of fuel over a ten hour flight or roughly five gallons per mile.  Aircrafts comprised nine percent of the United States' transportation sector's carbon emissions and three percent of country's total carbon emissions for 2013, according to the Center For Climate and Energy Solutions. Transportation is second only to the power sector as the country's largest CO2 emitter. Emissions from United States aircraft make up 29 percent of the world's aircraft emissions. If global aviation were a country, it would rank as the seventh largest carbon emitter in the world, according to the International Council on Clean Transportation.

The Montreal agreement comes after 73 out of 195 countries ratified the December 2015 Paris Climate Agreement aiming to regulate global emissions and curb global warming.