Reuters
A 43-page study by the International Council on Clean Transportation found that Norwegian Air Shuttle ASA, German-based Air Berlin and Ireland's national flag carrier Aer Lingus had the smallest carbon footprints among 20 transatlantic carriers in 2014.
British Airways, Scandinavian airline SAS and Deutsche Lufthansa AG had the worst CO2 performance, as measured by passenger mile (km) per quart (liter) of fuel.
Researchers were surprised by the 51 percent gap between top-rated Norwegian Air Shuttle and last-place British Airways, which is more than double that among U.S. airlines.