While U.S. intelligence agencies scour the world for a Boeing 727 that disappeared from Angola last month, aviation experts are scratching their heads trying to come up with another instance of a vanishing jetliner.
Alan Diehl, a former National Transportation Safety Board investigator, came up with just one very short-lived example, also from Africa.
He remembers a time when he was asked to help locate a giant Soviet transport plane that had disappeared en route from Mozambique to the tiny country of Swaziland.
It turned out one of the pilots had made a navigation mistake, and the plane was missing only for a few hours.
"I suspect things haven't changed that much," Diehl said. "All things are possible in Africa. It's extremely casual from a safety standpoint."
However, the Boeing 727 from Angola has been missing for more than three weeks — and aviation experts say that is extremely unusual.
"It's extremely rare for a plane, especially of that size, to disappear without a trace," Diehl said.
John Mazor of the Air Line Pilots Association said the pilots' union "could not come up with any examples of a commercial airliner just disappearing with no evidence of an accident."
"There've been one or two cases where an aircraft had disappeared, but it was under circumstances that gave a strong presumption it had crashed into the sea," Mazor said.
Aviation authorities have considered the odds of an airliner just vanishing into thin air to be so remote that emergency locator transmitters — standard equipment on small planes to help find them in the event of a crash — are not installed on large aircraft, said Ira J. Furman, a former NTSB director.
Airliners like 727s haven't been provided with the devices "on the theory that we don't lose them," Furman said.
It's particularly difficult to make a 153-foot, 95-ton 727 disappear, said Denis Chagnon of the International Civil Aviation Organization in Montreal. The sheer size of a 727 not only affects its visibility, but the amount of the maintenance it needs. "The larger the plane, the more complex the maintenance," he said.
Older planes also need more maintenance, and the 727 has largely been phased out. The 727 also has three engines and requires a flight crew of three, whereas most planes today have two engines and a crew of two.
Given all these factors, there almost always is a paper trail that prevents an airliner from disappearing completely, Chagnon said. "It's a very tight system," he said.
Reasons May Point to Results
If planes disappear under illicit circumstances, they're usually smaller, Chagnon said. Not only are they easier to maintain and harder to detect, but they usually have an easier time flying under radar.
On the other hand, a plane might be taken by someone scavenging for parts or "stolen" so that the owner can collect insurance money.
"The people who are most interested in [stolen planes] are insurance companies," Chagnon said.
"It's extremely possible this airplane was taken for parts," said Furman.