In late May, a Boeing 727 that had been parked on the Luanda airport tarmac for 14 months lumbered into the Angolan skies and vanished. Nearly a month later, the whereabouts of that plane are still unknown. There is much mystery in African aviation -- the paperwork on many aircraft is questionable -- but experts are particularly concerned in light of recent warnings about loose radiological material that could be fashioned into a "dirty bomb" -- conventional explosives packed with radioactive materials -- and used for terror attacks. The need for heightened security for radioactive materials is plain, but to be effective, antiterrorism programs will also have to crack down on delivery systems.

The history of the missing Boeing is a tangled affair, with a cast of characters that includes marijuana smugglers and convicted frauds. Who took the plane and where it was taken are unclear, but the last owner reportedly replaced the seats with fuel tanks before it disappeared -- an ominous-looking move in the aftermath of 9/11. While this could be run of the mill criminal behavior in the Byzantine world of aircraft sales, it might be something worse.

While terrorist strikes in the developed world have been the focus of most international concern, Africa has frequently been a target. The U.S. embassies in Tanzania and Kenya -- and hundreds of local citizens -- were early casualties in al-Qaeda's war against the West. Last year, terrorists launched attacks against Israeli targets in Kenya as well. Last month, Britain suspended flights to and from Kenya after warnings that they could be attacked. Weeks ago, blasts in Morocco killed dozens of innocent people. Al-Qaeda is suspected to have been behind them.