Efforts to reach the world's first climate deal governing the aviation sector got under way at a conference in Montreal.

Delegates to the U.N. International Civil Aviation Organization general assembly are being asked to approve, in two weeks, a program for the industry to become carbon neutral after 2020 and to halve net emissions by 2050 compared to 2005. Canadian Transportation Minister Marc Garneau said Tuesday strong that approval by the 191 participating countries will send a strong signal to other sectors.

So far, an estimated 58 ICAO countries have agreed to provide their support. Some including India, have voiced concerns. Aviation accounts for two percent of global greenhouse emissions but air travel is expected to double by 2030.

Environmental groups say the proposal doesn't go far enough.