When Dutch airline KLM launched adverts urging customers to "fly responsibly" and think about the environmental impact before booking a flight, it said it was showing its commitment to a sustainable future.

But the 2019 campaign sparked criticism and last year environmental activists filed a suit accusing the company of "greenwashing," or making misleading environmental claims.

The case filed by Fossil Free Netherlands highlights the dilemma facing airlines as they try to boost growth for shareholders but also convince the public they are taking steps to cut carbon emissions.