A United Nations accord to limit emissions from international air travel appeared to move toward becoming the first global climate accord targeting a single industry.

After nine days of debate in Montreal, the president of the UN’s aviation agency told delegates from 190 nations to bring final objections to him by 8 a.m. local time on Thursday in preparation to approve the measure. Under the agreement, companies would offset emissions growth after 2020 by funding environmental initiatives.

Still the outcome remains uncertain. While the deal has backing from at least 60 nations, including the U.S. and most of Europe, it has drawn objections from India, Russia and Brazil, which argue the measure would unfairly penalize developing countries with fast-growing aviation sectors.

The UN’s International Civil Aviation Organization estimates the agreement would cost airlines between $5.3 billion and $23.9 billion by 2035. Exhaust from international flights accounts for about 2 percent of global greenhouse gases, yet was largely omitted from the Paris accord on climate change last year because delegates feared divvying up responsibility for global routes could derail the broader deal.

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Photo Credit: An Air India Airlines Boeing 787 Dreamliner takes part in a flying display during the 50th Paris Air Show at the Le Bourget airport near Paris, June 14, 2013. India, Russia and Brazil have criticized a proposed UN emissions accord on international flights for unfairly crimping economies with emerging aviation sectors. Pascal Rossignol / Reuters