Earlier quoted context omitted.
These parts of the article provides plausible explanation: "Brian Jenkins, an aviation-security expert at the Rand Corp., said the nature of the security measure suggested that it was driven by intelligence of a possible attack." "The ban would begin just before Wednesday's meeting of the U.S.-led coalition against the Islamic State group in Washington. A number of top Arab officials were expected to attend the State…
What kind of attack would this policy avert?
(just guessing, if at all "it was driven by intelligence of a possible attack")