You'd never guess where they've found it now:
Israel grounds F16s over cancer concerns
"Israel has suspended training flights on US-made F-16 I fighters after finding a cancer-causing substance in the cockpit, the air force announced on Friday.
"The decision was taken "after pilots complained of a nauseating smell in the cockpit," the air force said in a statement.
"Tests detected the presence of formaldehyde, which is considered a carcinogen."