After a public outcry, Congress in late 2011 forced the FAA to reverse course and allow aircraft owners to block their flight information for any reason.

WSJ: Why Private-Jet Owners Don't Want to Be Tracked

In a statement, the FAA said it asked for "limited information" from those seeking to block their flight data for security reasons, and granted all such requests if they contained the required information.

WSJ: Why Private-Jet Owners Don't Want to Be Tracked

If a card belonging to a Berliner has never been used to purchase a plane ticket or buy goods outside Germany, the system may block an attempt to book a Moscow-Tokyo flight leaving in three hours.

ECONOMIST: Computing

An injection of Kuwaiti and Saudi capital has so far matched the flight of Syrian capital, but bankers fear that angry rulers in Damascus may block Lebanon's trade routes to the Arab world.

ECONOMIST: Lebanon