“The Federal Aviation Administration [FAA] said U.S. crop-duster planes could fly again after they were grounded for two days because of concern they could be used in a chemical or biological attack. The FAA had grounded all crop-duster planes since Sunday [September 23, 2001] after the FBI received information about the possibility of attacks using such aircraft. U.S. Atty. Gen. John Ashcroft said one of the suspected hijackers involved in the attack in New York was gathering information on the use of crop-dusting aircraft before the Sept. 11 attacks.”
– Times Wire Reports, “Ban on Crop-Duster Planes Lifted by FAA,” The Los Angeles Times, Sep. 26, 2001