I regularly say that security decisions are primarily made for non-security reasons. This article about the placement of sky marshals on airplanes is an excellent example. Basically, the airlines would prefer they fly coach instead of first class.

Airline CEOs met recently with TSA administrator John Pistole and officials from the Federal Air Marshal Service requesting the TSA to reconsider the placement of marshals based on current security threats.

“Our concern is far less revenue and more that we have defenses appropriate to the threat,” said James May, chief executive of the Air Transport Association, the airline industry’s lobbying group. “We think there needs to be an even distribution, particularly when we have multiple agents on board.”

[…]

By law, airlines must provide seats to marshals at no cost in any cabin requested. With first-class and business-class seats in particular, the revenue loss to airlines can be substantial because they can’t sell last-minute tickets or upgrades, and travelers sometimes get bumped to the back or lose out on upgrade opportunities. When travelers do get bumped, airlines are barred from divulging why the first-class seat was unexpectedly taken away, to keep the presence of a marshal a secret. Bumped travelers — airlines can’t disclose how many passengers are affected — typically get coach seats and refunds on the cash or miles they paid for the better seat.