The British defense ministry is being sued over claims some of its military helicopters exposed troops to toxic fumes that caused cancer, but the ministry failed to protect personnel for years, according to a report. The Times reports that both serving and former aircrew are allegedly dying or have died as a result of the diseases caused by choppers including Sea King—a model of helicopter which Prince William piloted during his time serving in the Royal Air Force Search and Rescue Force, according to MailOnline. Among those who have already received an out-of-court settlement related to the issue is Zach Stubbings, a former flight sergeant and helicopter winchman who reportedly trained alongside the Prince of Wales. Almost 40 people affected by the issue—which allegedly also involves fumes from other helicopters including Chinook—are now suing the U.K. Ministry of Defence. At least three people have already died and their families are now pursuing claims on their behalf, according to The Times.