Mali - In early 2008, an official at the U.S. Department of Homeland Security sent a report to his superiors detailing what he called the most significant development in the criminal exploitation of aircraft since 9/11.

The document warned that a growing fleet of rogue jet aircraft was regularly crisscrossing the Atlantic Ocean. On one end of the air route, it said, are cocaine-producing areas in the Andes controlled by the leftist Revolutionary Armed Forces of Colombia. On the other are some of West Africa's most unstable countries.

The report, a copy of which was obtained by Reuters, was ignored, and the problem has since escalated into what security officials in several countries describe as a global security threat.

The clandestine fleet has grown to include twin-engine turboprops, executive jets and retired Boeing 727s that are flying multi-ton loads of cocaine and possibly weapons to an area in Africa where factions of al Qaeda are believed to be facilitating the smuggling of drugs to Europe, the officials say.

Al Qaeda in the Islamic Maghreb (AQIM) has been held responsible for car and suicide bombings in Algeria and Mauritania.

Gunmen and bandits with links to AQIM have also stepped up kidnappings of Europeans for ransom, who are then passed on to AQIM factions seeking ransom payments.

The aircraft hopscotch across South American countries, picking up tons of cocaine and jet fuel, officials say. They then soar across the Atlantic to West Africa and the Sahel, where the drugs are funneled across the Sahara Desert and into Europe.

An examination of documents and interviews with officials in the United States and three West African nations suggest that at least 10 aircraft have been discovered using this air route since 2006. Officials warn that many of these aircraft were detected purely by chance. They caution that the real number involved in the networks is likely considerably higher.

Alexandre Schmidt, regional representative for West and Central Africa for the UN Office on Drugs and Crime, cautioned in Dakar this week that the aviation network has expanded in the past 12 months and now likely includes several Boeing 727 aircraft.

When you have this high capacity for transporting drugs into West Africa, this means that you have the capacity to transport as well other goods, so it is definitely a threat to security anywhere in the world, said Schmidt.

The other goods officials are most worried about are weapons that militant organizations can smuggle on the jet aircraft. A Boeing 727 can handle up to 10 tons of cargo.

The U.S. official who wrote the report for the Department of Homeland Security said the al Qaeda connection was unclear at the time.

The official is a counter-narcotics aviation expert who asked to remain anonymous as he is not authorized to speak on the record. He said he was dismayed by the lack of attention to the matter since he wrote the report.

You've got an established terrorist connection on this side of the Atlantic. Now on the Africa side you have the al Qaeda connection and it's extremely disturbing and a little bit mystifying that it's not one of the top priorities of the government, he said.

Since the September 11 attacks, the security system for passenger air traffic has been ratcheted up in the United States and throughout much of the rest of the world, with the latest measures imposed just weeks ago after a failed bomb attempt on a Detroit-bound plane on December 25.

The bad guys have responded with their own aviation network that is out there everyday flying loads and moving contraband, said the official, and the government seems to be oblivious to it.

The upshot, he said, is that militant organizations -- including groups like the FARC and al Qaeda -- have the power to move people and material and contraband anywhere around the world with a couple of fuel stops.

The lucrative drug trade is already having a deleterious impact on West African nations. Local authorities told Reuters they are increasingly outgunned and unable to stop the smugglers.

And significantly, many experts say, the drug trafficking is bringing in huge revenues to groups that say they are part of al Qaeda. It's swelling not just their coffers but also their ranks, they say, as drug money is becoming an effective recruiting tool in some of the world's most desperately poor regions.

U.S. President Barack Obama has chided his intelligence officials for not pooling information to connect those dots to prevent threats from being realized. But these dots, scattered across two continents like flaring traces on a radar screen, remain largely unconnected and the fleets themselves are still flying.

THE AFRICAN CONNECTION

The deadly cocaine trade always follows the money, and its cash-flush traffickers seek out the routes that are the mostly lightly policed.

Beset by corruption and poverty, weak countries across West Africa have become staging platforms for transporting between 30 tons and 100 tons of cocaine each year that ends up in Europe, according to U.N. estimates.

Drug trafficking, though on a much smaller scale, has existed here and elsewhere on the continent since at least the late 1990s, according to local authorities and U.S. enforcement officials.

Earlier this decade, sea interdictions were stepped up. So smugglers developed an air fleet that is able to transport tons of cocaine from the Andes to African nations that include Mauritania, Mali, Sierra Leone and Guinea Bissau.What these countries have in common are numerous disused landing strips and makeshift runways -- most without radar or police presence. Guinea Bissau has no aviation radar at all. As fleets grew, so, too, did the drug trade.

The DEA says all aircraft seized in West Africa had departed Venezuela. That nation's location on the Caribbean and Atlantic seaboard of South America makes it an ideal takeoff place for drug flights bound for Africa, they say.

A number of aircraft have been retrofitted with additional fuel tanks to allow in-flight refueling -- a technique innovated by Mexico's drug smugglers. (Cartel pilots there have been known to stretch an aircraft's flight range by putting a water mattress filled with aviation fuel in the cabin, then stacking cargoes of marijuana bundles on top to act as an improvised fuel pump.)

Ploys used by the cartel aviators to mask the flights include fraudulent pilot certificates, false registration documents and altered tail numbers to steer clear of law enforcement lookout lists, investigators say. Some aircraft have also been found without air-worthiness certificates or log books. When smugglers are forced to abandon them, they torch them to destroy forensic and other evidence like serial numbers.

The evidence suggests that some Africa-bound cocaine jets also file a regional flight plan to avoid arousing suspicion from investigators. They then subsequently change them at the last minute, confident that their switch will go undetected.

One Gulfstream II jet, waiting with its engines running to take on 2.3 tons of cocaine at Margarita Island in Venezuela, requested a last-minute flight plan change to war-ravaged Sierra Leone in West Africa. It was nabbed moments later by Venezuelan troops, the report seen by Reuters showed.

Once airborne, the planes soar to altitudes used by commercial jets. They have little fear of interdiction as there is no long-range radar coverage over the Atlantic. Current detection efforts by U.S. authorities, using fixed radar and P3 aircraft, are limited to traditional Caribbean and north Atlantic air and marine transit corridors.

The aircraft land at airports, disused runways or improvised air strips in Africa. One bearing a false Red Cross emblem touched down without authorization onto an unlit strip at Lungi International Airport in Sierra Leone in 2008, according to a U.N. report.

Late last year a Boeing 727 landed on an improvised runway using the hard-packed sand of a Tuareg camel caravan route in Mali, where local officials said smugglers offloaded between 2 and 10 tons of cocaine before dousing the jet with fuel and burning it after it failed to take off again.

For years, traffickers in Mexico have bribed officials to allow them to land and offload cocaine flights at commercial airports. That's now happening in Africa as well. In July 2008, troops in coup-prone Guinea Bissau secured Bissau international airport to allow an unscheduled cocaine flight to land, according to Edmundo Mendes, a director with the Judicial Police.

When we got there, the soldiers were protecting the aircraft, said Mendes, who tried to nab the Gulfstream II jet packed with an estimated $50 million in cocaine but was blocked by the military.

The soldiers verbally threatened us, he said. The cocaine was never recovered. Just last week, Reuters photographed two aircraft at Osvaldo Vieira International Airport in Guinea Bissau -- one had been dispatched by traffickers from Senegal to try to repair the other, a Gulfstream II jet, after it developed mechanical problems. Police seized the second aircraft.

FLYING BLIND

One of the clearest indications of how much this aviation network has advanced was the discovery, on November 2, of the burned out fuselage of an aging Boeing 727. Local authorities found it resting on its side in rolling sands in Mali. In several ways, the use of such an aircraft marks a significant advance for smugglers.

Boeing jetliners, like the one discovered in Mali, can fly a cargo of several tons into remote areas. They also require a three-man crew -- a pilot, co pilot and flight engineer, primarily to manage the complex fuel system dating from an era before automation.

Hundreds of miles to the west, in the sultry, former Portuguese colony of Guinea Bissau, national Interpol director Calvario Ahukharie said several abandoned airfields, including strips used at one time by the Portuguese military, had recently been restored by drug mafias for illicit flights.

In the past, the planes coming from Latin America usually landed at Bissau airport, Ahukharie said as a generator churned the feeble air-conditioning in his office during one of the city's frequent blackouts.

But now they land at airports in southern and eastern Bissau where the judicial police have no presence.

Ahukharie said drug flights are landing at Cacine, in eastern Bissau, and Bubaque in the Bijagos Archipelago, a chain of more than 80 islands off the Atlantic coast. Interpol said it hears about the flights from locals, although they have been unable to seize aircraft, citing a lack of resources.

The drug trade, by both air and sea, has already had a devastating impact on Guinea Bissau. A dispute over trafficking has been linked to the assassination of the military chief of staff, General Batista Tagme Na Wai in 2009. Hours later, the country's president, Joao Bernardo Vieira, was hacked to death by machete in his home.

Asked how serious the issue of air trafficking remained for Guinea Bissau, Ahukharie was unambiguous: The problem is grave.

The situation is potentially worse in the Sahel-Sahara, where cocaine is arriving by the ton. There it is fed into well-established overland trafficking routes across the Sahara where government influence is limited and where factions of al Qaeda in the Islamic Maghreb have become increasingly active.

The group, previously known as the Salafist Group for Preaching and Combat, is raising millions of dollars from the kidnap of Europeans.

Analysts say militants strike deals of convenience with Tuareg rebels and smugglers of arms, cigarettes and drugs. According to a growing pattern of evidence, the group may now be deriving hefty revenues from facilitating the smuggling of FARC-made cocaine to the shores of Europe.

UNHOLY ALLIANCE

In December, Antonio Maria Costa, the executive director of the UN Office on Drugs and Crime, told a special session of the UN Security Council that drugs were being traded by terrorists and anti-government forces to fund their operations from the Andes, to Asia and the African Sahel.

In the past, trade across the Sahara was by caravans, he said. Today it is larger in size, faster at delivery and more high-tech, as evidenced by the debris of a Boeing 727 found on November 2nd in the Gao region of Mali -- an area affected by insurgency and terrorism.

Just days later, U.S. Drug Enforcement Administration officials arrested three West African men following a sting operation in Ghana. The men, all from Mali, were extradited to New York on December 16 on drug trafficking and terrorism charges.

Oumar Issa, Harouna Toure, and Idriss Abelrahman are accused of plotting to transport cocaine across Africa with the intent to support al Qaeda, its local affiliate AQIM and the FARC. The charges provided evidence of what the DEA's top official in Colombia described to a Reuters reporter as an unholy alliance between South American narco-terrorists and Islamic extremists.

Some experts are skeptical, however, that the men are any more than criminals. They questioned whether the drug dealers oversold their al Qaeda connections to get their hands on the cocaine.

In its criminal complaint, the DEA said Toure had led an armed group affiliated to al Qaeda that could move the cocaine from Ghana through North Africa to Spain for a fee of $2,000 per kilo for transportation and protection.

Toure discussed two different overland routes with an undercover informant. One was through Algeria and Morocco; the other via Algeria to Libya. He told the informer that the group had worked with al Qaeda to transport between one and two tons of hashish to Tunisia, as well as smuggle Pakistani, Indian and Bangladeshi migrants into Spain.

In any event, AQIM has been gaining in notoriety. Security analysts warn that cash stemming from the trans-Saharan coke trade could transform the organization -- a small, agile group whose southern-Sahel wing is estimated to number between 100 and 200 men -- into a more potent threat in the region that stretches from Mauritania to Niger. It is an area with huge foreign investments in oil, mining and a possible trans-Sahara gas pipeline.

These groups are going to have a lot more money than they've had before, and I think you are going to see them with much more sophisticated weapons, said Douglas Farah, a senior fellow at the International Assessment Strategy Center, a Washington based security think-tank.

NARCOTIC INDUSTRIAL DEPOT

The Timbuktu region covers more than a third of northern Mali, where the parched, scrubby Sahel shades into the endless, rolling dunes of the Sahara Desert. It is an area several times the size of Switzerland, much of it beyond state control.

Moulaye Haidara, the customs official, said the sharp influx of cocaine by air has transformed the area into an industrial depot for cocaine.

Sitting in a cool, dark, mud-brick office building in the city where nomadic Tuareg mingle with Arabs and African Songhay, Fulani and Mande peoples, Haidara expresses alarm at the challenge local law enforcement faces.

Using profits from the trade, the smugglers have already bought automatic weapons, and they are very determined, Haidara said. He added that they call themselves Al Qaeda, though he believes the group had nothing to do with religion, but used it as an ideological base.

Local authorities say four-wheel-drive Toyota SUVs outfitted with GPS navigation equipment and satellite telephones are standard issue for smugglers. Residents say traffickers deflate the tires to gain better traction on the loose Saharan sands, and can travel at speeds of up to 70 miles-per-hour in convoys along routes to North Africa.

Timbuktu governor, Colonel Mamadou Mangara, said he believes traffickers have air-conditioned tents that enable them to operate in areas of the Sahara where summer temperatures are so fierce that they scorch your shoes. He added that the army lacked such equipment. A growing number of people in the impoverished region, where transport by donkey cart and camel are still common, are being drawn to the trade. They can earn 4 to 5 million CFA Francs (roughly $9-11,000) on just one coke run.

Smuggling can be attractive to people here who can make only $100 or $200 a month, said Mohamed Ag Hamalek, a Tuareg tourist guide in Timbuktu, whose family until recently earned their keep hauling rock salt by camel train, using the stars to navigate the Sahara.

Haidara described northern Mali as a no-go area for the customs service. There is now a red line across northern Mali, nobody can go there, he said, sketching a map of the country on a scrap of paper with a ballpoint pen. If you go there with feeble means ... you don't come back.

TWO-WAY TRADE

Speaking in Dakar this week, Schmidt, the U.N. official, said that growing clandestine air traffic required urgent action on the part of the international community.

This should be the highest concern for governments ... For West African countries, for West European countries, for Russia and the U.S., this should be very high on the agenda, he said.

Stopping the trade, as the traffickers are undoubtedly aware, is a huge challenge -- diplomatically, structurally and economically.

Venezuela, the takeoff or refueling point for aircraft making the trip, has a confrontational relationship with Colombia, where President Alvaro Uribe has focused on crushing the FARC's 45-year-old insurgency. The nation's leftist leader, Hugo Chavez, won't allow in the DEA to work in the country.

In a measure of his hostility to Washington, he scrambled two F16 fighter jets last week to intercept an American P3 aircraft -- a plane used to seek out and track drug traffickers -- which he said had twice violated Venezuelan airspace. He says the United States and Colombia are using anti-drug operations as a cover for a planned invasion of his oil-rich country. Washington and Bogota dismiss the allegation.

In terms of curbing trafficking, the DEA has by far the largest overseas presence of any U.S. federal law enforcement, with 83 offices in 62 countries. But it is spread thin in Africa where it has just four offices -- in Nigeria, Ghana, Egypt and South Africa -- though there are plans to open a fifth office in Kenya.

Law enforcement agencies from Europe as well as Interpol are also at work to curb the trade. But locally, officials are quick to point out that Africa is losing the war on drugs.

The most glaring problem, as Mali's example shows, is a lack of resources. The only arrests made in connection with the Boeing came days after it was found in the desert -- and those incarcerated turned out to be desert nomads cannibalizing the plane's aluminum skin, probably to make cooking pots. They were soon released.

Police in Guinea Bissau, meanwhile, told Reuters they have few guns, no money for gas for vehicles given by donor governments and no high security prison to hold criminals.

Corruption is also a problem. The army has freed several traffickers charged or detained by authorities seeking to tackle the problem, police and rights groups said.

Serious questions remain about why Malian authorities took so long to report the Boeing's discovery to the international law enforcement community.

What is particularly worrying to U.S. interests is that the networks of aircraft are not just flying one way -- hauling coke to Africa from Latin America -- but are also flying back to the Americas.

The internal Department of Homeland Security memorandum reviewed by Reuters cited one instance in which an aircraft from Africa landed in Mexico with passengers and unexamined cargo.

The Gulfstream II jet arrived in Cancun, by way of Margarita Island, Venezuela, en route from Africa. The aircraft, which was on an aviation watch list, carried just two passengers. One was a U.S. national with no luggage, the other a citizen of the Republic of Congo with a diplomatic passport and a briefcase, which was not searched.

The obvious huge concern is that you have a transportation system that is capable of transporting tons of cocaine from west to east, said the aviation specialist who wrote the Homeland Security report.

But it's reckless to assume that nothing is coming back, and when there's terrorist organizations on either side of this pipeline, it should be a high priority to find out what is coming back on those airplanes.

(Additional reporting by Tiemoko Diallo in Mali, Alberto Dabo in Guinea Bissau and Hugh Bronstein in Colombia, editing by Jim Impoco and Claudia Parsons)

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