French carrier Air France will offset the carbon dioxide emissions of its 500-odd daily internal flights by 2020 at a cost of millions of euros, the company's CEO has announced.

In a bid to counteract its climate impact, the company will finance projects that support tree planting, forest protection and the global shift to less polluting energy, Anne Rigail told Le Parisien newspaper.

"It is an investment of several million euros, she said in an interview published late Monday, adding the company was acting "voluntarily".

Other projects would include banning single-use plastics such as cutlery from local flights as from January, and "to start separating and recycling waste" from October.

The airline industry has been under fire over its carbon emissions, which at 285 grammes of CO2 emitted per kilometre travelled by each passenger, far exceed all other modes of transport, according to the European Environment Agency.

Heavy duty transportation -- freight trucking, shipping and aviation -- represent over a tenth of global greenhouse gas emissions, says the World Resources Institute, a research body.

The emissions contribute to global warming and climate change, which scientists say will unleash ever harsher droughts, superstorms, and sea-level rise.

In July, France announced it would impose new taxes on plane tickets of between 1.50 and 18 euros per flight -- a move criticised by Air France.

It is meant to raise about 180 million euros a year to be invested in greener transport infrastructure.

Rigail said she did not know if there had been a drop in passenger numbers due to a campaign of "flight shaming" (flygskam) spearheaded by 16-year-old schoolgirl Greta Thunberg, who has become a symbol of the fight against climate change.