676 F-15s, including mission critical jets, was grounded on November 3

Maj. Cristin Marposon, an Air Force spokeswoman, told The Associated Press the country's fleet of 676 F-15s, including mission critical jets, was grounded on November 3 for "air worthiness concerns"
http://www.cnn.com/2007/US/11/05/f15.grounding/index.html