As President Bush signed a bill delivering $15 billion in federal aid to the nation’s ailing airlines this weekend, alarming news surfaced of possible new terrorist attacks from the skies. Concerned about possible chemical weapons attacks, the Federal Aviation Administration imposed a one-day ban Sunday on crop-dusting from airplanes in domestic airspace. Sunday’s stand-down marked the second time that agricultural pilots have been told not to fly since the Sept. 11 attacks. Asked by the reporters about the new grounding, the FBI said it was one of the steps the bureau has taken out of “an abundance of caution” and “in reaction to every bit of information and threats received during the course of this investigation.” Meanwhile, investigators continued their sweep for terrorists within America. In a Dallas suburb, the FBI arrested a Palestinian whose name turned up in the address book of a former personal secretary to bin Laden. Ghassan Dahduli is appealing an immigration court deportation ruling for fraudulently obtaining a work visa, FBI spokeswoman Lori Bailey told Reuters. In Austin, Texas, authorities pulled from an American Airlines flight two men whose names matched those on an FBI list of people wanted for questioning. The passengers were detained while boarding, said John Hotard, a spokesman for American Airlines. Meanwhile, The New York Times on Sunday reported that European, American and Pakistani officials say that they have identified new elements of the bin Laden terrorist network, including a top lieutenant in Europe and a previously undisclosed cell in the Gaza Strip. At least 11,000 terrorists have been trained in the past five years at camps operated by bin Laden in Pakistan, officials tell The Times — which points out that these terrorists have been dispatched so far and wide that eliminating their training camps, or even bin Laden, may only be part of the solution.