A sign is shown posted on a perimeter fence near Delta 747 aircraft taxiing at the Detroit Metropolitan Airport in Romulus, Mich., Thursday, April 9, 2015. The security fences and perimeter gates at Detroit Metropolitan Airport have been breached four times in the past two years, an Associated Press investigation shows. Nationally, at least 268 such breaches occurred at 31 major U.S. airports since the start of 2004.
A sign is shown posted on a perimeter fence near Delta 747 aircraft taxiing at the Detroit Metropolitan Airport in Romulus, Mich., Thursday, April 9, 2015. The security fences and perimeter gates at Detroit Metropolitan Airport have been breached four times in the past two years, an Associated Press investigation shows. Nationally, at least 268 such breaches occurred at 31 major U.S. airports since the start of 2004. Paul Sancya AP
A sign is shown posted on a perimeter fence near Delta 747 aircraft taxiing at the Detroit Metropolitan Airport in Romulus, Mich., Thursday, April 9, 2015. The security fences and perimeter gates at Detroit Metropolitan Airport have been breached four times in the past two years, an Associated Press investigation shows. Nationally, at least 268 such breaches occurred at 31 major U.S. airports since the start of 2004. Paul Sancya AP