previously , the u.s. did not disclose whether a stopped traveler was on the list or why .
but facing legal pressure from the aclu , the obama administration has enacted a new policy to let americans know if they are on the list .
grounded americans are also now allowed to inquire about how they got on the list .
however , the government has not promised to reveal why in all cases - citing possible national security threats .
last fall there were about 64,000 people on the no-fly list , and americans made up approximately 5 per cent .