The Associated Press reports that the federal government's list of those who are banned from flying in or to the United States has more than doubled in the last year, to 21,000 names. About 500 of the people on that list are Americans. The government refuses to disclose the list or how someone ends up on it, but officials admit that the criteria for making the list has expanded — particularly since the attempted "underwear bombing" in 2009 —  to include anyone who might pose any threat, not just a specific threat to airplanes.

The AP story written by Eileen Sullivan seems to paint the expansion as an Obama administration problem, stating that "the government lowered the bar for being added to the list, even as it says it's closer than ever to defeating al-Qaida." But near the bottom of the story, it admits that the no-fly list had ballooned to 20,000 back in 2004. That means that at some point in the intervening six years, the list was halved. Whether that was done by the Bush or Obama administrations (or both) is unknown. 

In fact, a lot is not-known about the list, which is part of the problem. Even those who are on it cannot find if they are on it, unless they attempt to fly and are denied. One of the other changes appears to be the allowance of "single sourcing" of evidence to get someone's name on the list. The father of the man who attempted that Christmas Day bombing warned the U.S. embassy in Nigeria about his son, but under the old rules, that single accusation wasn't enough to warrant putting the son on the no-fly list. Now, if the father was considered a credible source, that would be enough. Transportation Security Administrator John Pistole says that intelligence and law enforcement are continually adding new threats to the list.