The TSA no fly list has somewhere between 2500 and 3400 names on it. There are some 400,000 potential terrorists on various lists circulating around the several intelligence agencies that deal with terror. Why not put all 400,000 names on the no fly list?
Probably most of the 400,000 are not terrorists and we have nothing to fear from them. I suspect most are Muslims. But still, their names have come to official attention for some reason. So there is probably some sort of terrorist connection, however tentative.
Inconveniencing these 400,000 Muslims by not allowing them to fly will cause some of them question Islam’s place in the world. Maybe a few of them would ask themselves why Muslims are not allowed on planes and are regarded with suspicion and dislike throughout much of the world.
That will lead to some reflection about their religion and about how some of its practitioners behave that causes the rest of the world to dislike them. Maybe a seed of self doubt will be planted and it will grow into a tree of reform from within the religion.