‘Poisoned planes’ It has been called the biggest scandal and the best-kept secret in the aviation world: the toxic substances that crew members and passengers potentially inhale through the air conditioning on board aircraft. According to experts, poisoning results from oil leaks in the engine. These leaks may cause TCP, a toxic component in oil, to be released into the air conditioning system. Sometimes, the presence of toxic fumes is impossible to detect and amounts are minimal. In other cases, a ‘fume event’ occurs and a cloud of noxious odour and smoke fills the cockpit, cabin or both.