An 18-month investigation has resulted in the arrests of 40 Northern California pilots who may have been flying with debilitating illnesses that should have kept them grounded, the U.S. Attorney's office said.
Illnesses ranged from schizophrenia and bipolar disorder to drug and alcohol addiction and heart conditions — all of which would disqualify them from holding a medical certificate, which is necessary to maintain a valid pilot's license.
http://www.usatoday.com/travel/news/2005-07-19-pilots-lied_x.htm