Lost property rarely comes as big as this. On a sleepy Sunday evening, a Boeing 727 suddenly fires its engines and jerks out of its space in the Angolan capital, Luanda. Shocked airtraffic controllers frantically radio the plane to call it back.
The pilot, a mystery man who boarded minutes earlier, ignores them. Roaring up the runway, the plane soars into the African night. Since then, as one American official put it, nobody has seen "hide nor hair" of the missing jet.
It could be a spectacular theft or simply a financial scam. But the disappearance of the aircraft almost four weeks ago has alarmed the US, which fears it could be used in an11 September-style attack on American targets in Africa.
The CIA has activated spy satellites in a continent-wide search for the plane, recently converted from a passenger jet into a fuel tanker. Airstrips are being scanned while US embassies across Africa are enquiring for other clues.
The search had turned up few leads so far, Ari Fleischer, the White House spokesman, admitted yesterday. "We don't have any reliable assessments about what this portends, what it could be, who may be behind it," he said.
A cloud of confusion surrounds the 727. Some reports suggest it headed for Burkina Faso, applied for permission to land on the opposite side of Africa in the Seychelles, and failed to land at either place.
The South African government denied that it landed in its territory. "If it had come south we would have known about it," Arthur Bradshaw, head of aeronautical search and rescue, told a Johannesburg radio station.
The disappearance has raised fears of a imminent terrorist attack in Africa. Last month a chain of orchestrated suicide bombings claimed 42 lives in Casablanca, Morocco. In November last year suspected al-Qa'ida bombers killed 15 people in Mombasa, Kenya.
Although the plane might have been stolen as part of a business dispute or by smugglers, US officials are worried that the tanker in effect, a flying bomb could fall into the hands of terrorists.
East Africa is on high alert. British Airways flights to Kenya remain suspended, while the US embassy in Nairobi often closes without notice because of what officials describe as "a very real, continuing threat of terrorist activity in Kenya and east Africa".
The 727 was operated by American Airlines until 2001, but its recent history is chequered. It officially belongs to Aerospace Sales and Leasing Co (ASL), a Miami-based company whose president, Maury Joseph, is a convicted fraudster. Mr Maury's son, Lance, told The Washington Post that ASL subsequently leased the plane to another, unnamed company which replaced the seats with fuel tanks to make deliveries to remote African airfields.
According to some reports, this company is Angola Air, a murky transporter with links both to the Angolan military and Victor Bout, an east European named by the United Nations as an arms and contraband smuggler in several African war zones. Before the US war against the Taliban, one of Mr Bout's companies ran an air service from the United Arab Emirates to Kandahar in Afghanistan, in contravention of a UN embargo.
Why would anyone want to steal the plane? According to local authorities, it had not left the apron in Luanda for the previous 14 months. It was grounded for having incorrect papers and for non-payment of £2.6m in airport ramp fees.
One theory is that the mystery pilot identified by Angola as a US citizen might have taken the plane to avoid payment of the dues, or for use in smuggling operations elsewhere in Africa.
Chris Yates, aviation security editor with Jane's Transport, said: "There's a substantial amount of illegal air operations in Africa, from gun running to arms smuggling. The aircraft could have been taken by one of those groups." But he added: "Until we get some more information, this is a complete and utter mystery."
One aircraft database suggested the plane was slated for export to Nicaragua, and then for eventual delivery to a Nigerian airline.
Angola's air transport ministry has promised a full and open investigation into the disappearance. But there is little optimism that it will solve the mystery. Angola's government is famously corrupt and its aerospace regulations notoriously lax. During the war with Unita rebels, Russian-piloted aircraft smuggled guns, diamonds and other contraband in and out of neighbouring countries. Of the six air companies registered in Angola, four have a record of illegal activities.
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