Ground-based vehicles have had emissions standards for a while (just ask Volkswagen), but commercial aircraft like passenger jets? Not so much. However, the world just took one big step toward cleaning up the skies: a total of 23 countries have agreed to set the first international carbon dioxide emissions standard for commercial aircraft. If the measures are adopted as recommended, new airplane models will have to meet the tougher guidelines in 2020. New aircraft from existing model lines will follow suit in 2023, and there will be a complete cutoff for non-standard aircraft in 2028.