FILE - In this Monday, Sept. 17, 2001 file picture, Robert Williams of Mihand Aircraft near England, Ark., places the engine cover back on his agricultural airplane after removing the battery cable. Federal officials allowed crop-spraying planes to return to the skies as long as they stayed away from commercial airports, one day after they were grounded because of security concerns after the previous week's terrorist attacks. On Friday, Sept. 2, 2011, the FBI and Homeland Security have issued a nationwide warning about al-Qaida threats to small airplanes, just days before the anniversary of the 2001 terrorist attacks. (AP Photo/Spencer Tirey, File)
{}