In July 2022, environmentalist groups, including Fossielvrij, ClientEarth and Reclame Fossielvrij, launched a lawsuit against KLM. The groups argue the company ran misleading adverts for its 2019 sustainability scheme called 'Fly Responsibly'. The programme, which KLM has since stopped, allowed consumers to 'offset' carbon emissions from their flights by funding reforestation projects or KLM biofuel purchases. The groups argue such marketing was environmentally misleading and breached EU consumer law. The groups are also challenging KLM's claim that the company is "creating a more sustainable future", as its goal to reach net zero emissions by 2050 contradicts KLM's plans for future growth.

In June 2023, the District Court of Amsterdam allowed Fossielvrij and Reclame Fossielvrij to bring the claim against KLM in court. The ruling marks the first instance a court allowed an environmental non-profit to bring a greenwashing case under a new Dutch class action law. The groups also assert the greenwashing lawsuit is the first to be brought against the airline industry.

In March 2024, KLM was found guilty of misleading customers with vague environmental claims. The court determined that KLM had violated the law with misleading advertising in 15 of 19 environmental statements, criticizing the airline for presenting an overly optimistic view of its sustainable aviation fuel initiatives and tree-planting efforts. KLM responded by stating that the communications addressed in the case had not been used for some time and expressed satisfaction that the court allowed them to continue communicating transparently about their sustainability efforts.