The skies above the U.S. military’s counterterrorism hub on the Horn of Africa have become chronically dangerous, with pilots forced to rely on local air-traffic controllers who fall asleep on the job, commit errors at astronomical rates and are hostile to Americans, documents show.

Conditions at Camp Lemonnier in Djibouti, the base for U.S. pilots flying sensitive missions over Yemen and Somalia, have become so dire that American warplanes and civilian airliners alike are routinely placed in jeopardy, according to federal aviation experts and documents obtained by The Washington Post under the Freedom of Information Act.

Unlike other major U.S. military bases around the world, Camp Lemonnier is wholly dependent on civilian air-traffic controllers, hired by the government of Djibouti to keep the skies safe. But as the base has increased in size and importance, the Djiboutian controllers’ hazardous habits and deep dislike for drones have disrupted U.S. military operations and triggered repeated warnings about the risk of an aviation catastrophe.

The military documents, based on observation reports from the flight tower, describe scenes that would be comic if not for the potential for disaster.

Some controllers habitually dozed on the floor while on duty, pulling a blanket over their heads to drown out radio traffic. Others immersed themselves in video games and personal phone calls while ignoring communication from pilots. Still others punished U.S. flight crews for a perceived lack of respect by forcing them to circle overhead until they ran low on fuel.  Within view of the air-traffic control tower at Camp Lemonnier, a Navy HS-60 Sea Hawk taxis onto the tarmac. (Master Sgt. Scott Wagers/U.S. Air Force)

A common vice in the flight tower was chewing khat, a leafy plant that acts as a stimulant and is banned in the United States but legal and popular in Djibouti, according to the documents.

Outsiders who tried to impose order did so at their peril. One Djiboutian supervisor was beaten up by a controller and tossed down the flight-tower stairs. A U.S. Navy officer was threatened with a pipe.

The documents chronicle an ill-fated $7 million U.S. program in which former Federal Aviation Administration officials were tapped to retrain the Djiboutian air-traffic controllers in 2012 and 2013. The effort collapsed after the Djiboutians stopped showing up for classes and locked the American trainers out of the flight tower.

[How the U.S. military built a secretive drone base on the Horn of Africa]

The controllers’ actions have exacerbated already difficult conditions at Camp Lemonnier, which shares its two runways with Djibouti’s only international airport, a French military base and a small contingent of Japanese military aircraft. As a result, the controllers must juggle civilian airliners with an unusual assortment of fighter planes, drones and cargo jets.

The U.S. military is the airport’s biggest user. It accounted for more than half of the 30,000 takeoffs and landings last year, military officials said.

In interviews, some of the former FAA officials said they were shocked that the U.S. military would tolerate such unsafe conditions.

“It’s mind-boggling,” said one former FAA official who spent nearly a year in Djibouti and spoke on the condition of anonymity out of fear of reprisals. “Literally, it’s the most dangerous airspace I’ve seen in the world, and I’ve been to Afghanistan.”

Although Camp Lemonnier is a joint base used by each branch of the U.S. armed forces, the Navy holds primary responsibility for its upkeep and protection.

Navy officials were slow to respond to queries about aviation safety hazards in Djibouti, taking more than 14 months to process The Post’s Freedom of Information Act request. They released the unclassified documents only after The Post said it would file a lawsuit.

The Navy heavily redacted the records, blacking out reports of narrowly averted collisions and mistake after mistake by the Djiboutian controllers. The Post obtained uncensored copies from a source upset about the military’s attempt to conceal the problems.

[What the Navy withheld from records about its base in Djibouti]

Navy Capt. Matthew P. O’Keefe, the commanding officer of Camp Lemonnier, played down the risks cited in the documents, saying they did not reflect current conditions.

He said the U.S. military had built a good relationship with Djiboutian officials but could not “impose our will on our partners” or on how they manage their airspace.

“We are here with their consent,” O’Keefe said. “We do our best to work closely with them to provide a safe environment.”

Other U.S. officials said the Obama administration has been pressing Djibouti in high-level talks to bolster aviation safety, given the Pentagon’s increasing reliance on Camp Lemonnier.

In addition to serving as a counterterrorism hub for Somalia and Yemen, the camp is the only permanent U.S. base in Africa, with about 4,000 personnel. Last year, the Obama administration signed a new lease with the Djiboutian government that will keep the U.S. military there for at least two more decades.

“We had indicated that we want to see further improvements in aviation,” said Tom Kelly, the U.S. ambassador to Djibouti. “What I want to know is, is this airport safe for us and our people to fly right now? I believe we’re making progress.”

The Djibouti government denied that there have been any safety shortcomings at the airport.

Issa Saher Bouraleh, a counselor at the Djiboutian Embassy in Washington, said the reports of controllers sleeping on the job, using khat and leaving the tower unattended were invented or exaggerated.

“That’s nonsense,” he said in an interview. “I’m sure that the airport is safe. It is more safe than other Arab countries.” If controllers were really sleeping on the tower floor or hooked on khat, he added, “there would be accidents every day.”

The Pentagon is in the midst of a $1.4 billion long-term project to upgrade Camp Lemonnier.

In addition to supporting conventional military missions in Africa and the Middle East, the base houses a large compound for the Joint Special Operations Command, which runs secretive counterterrorism operations.

From Djibouti, the U.S. military flies fighter jets, spy planes, cargo aircraft, helicopters and a large fleet of Predator and Reaper drones. They share airspace with major carriers such as Air France, Turkish Airlines, Qatar Airways and Ethio­pian Airlines.

There has been one fatal accident in Djibouti involving a U.S. military aircraft, along with several drone crashes and dozens of close calls, records show.

In February 2012, a small U-28 spy plane crashed a few miles from the airport, killing its four Special Operations crew members. Moments before, the Djiboutian controllers had denied the crew’s initial request to land and ordered it to circle the airfield.

An Air Force accident investigation board determined that the controllers were not to blame, but it heard lots of complaints from Air Force personnel.

“The air traffic control was dismal,” an unidentified U-28 pilot testified before the board. He said the controllers were “often aloof, sometimes asleep, sometimes hyper-aggressive.”

“Every time I flew, I did not understand why I was having to do this for an African controller that my government was giving money to,” the pilot testified. “Why am I having to rush myself to the ground? And oh, why am I almost out of gas? Why am I in this situation?”

In addition to the fatal accident, six U.S. drones based at Camp Lemonnier have been destroyed in crashes.

[Why military drones at civilian airports spell trouble]

Air Force investigators did not pin responsibility for any of the drone crashes on the flight tower. Again, however, Air Force drone crews fumed to investigators, saying the controllers were difficult to deal with.

One drone crew member said he would often have to repeat himself four or five times on the radio before he would get a response. “You didn’t know from day to day what you were going to get,” he said.

A drone unit commander said that the controllers were not sure how to direct remotely piloted aircraft and that the controllers often left them in limbo. “Now, we tend to hold a lot when we’re out of gas because they’re letting everybody else land ahead of us, just in case we have an accident.”

The former FAA officials said the Djiboutian controllers considered the drones unreliable aircraft and malign weapons for killing Muslims. On multiple occasions, they said, the controllers abruptly issued edicts declaring that drones were forbidden from taking off or landing.

The drone bans lasted no longer than a week but disrupted U.S. military operations.

“The Djiboutians’ greatest fears were these drones,” said one of the former FAA officials. “They hated these drones with a passion.”

Tensions over the drones became so severe that the U.S. military agreed to move the robotic aircraft in 2013 from Camp Lemonnier to a remote desert airstrip in another part of the country.

In an attempt to solve the broader air-traffic problem, the Navy in 2012 hired Washington Consulting Group, based in Bethesda, Md.

The aviation consultancy dispatched about a dozen air-traffic-control experts and former FAA officials to Djibouti with instructions to retrain the local controllers. They immediately faced resistance.

The Djiboutians insisted that they did not need refresher training. Within a few weeks, one controller temporarily booted the former FAA officials from the tower, according to the documents.

After some incentives were dangled — free lunch and a free iPad if they completed the course — the Djiboutians agreed to attend some classroom seminars. But attendance dwindled after they insisted on cash payments instead of lunch. Some controllers wanted the money to buy khat, which they used in a break room in the tower, the documents show.

After Navy officers intervened, Washington Consulting Group regained its access to the flight tower. Although the Djiboutians still maintained that they did not need on-the-job training, they reluctantly allowed one U.S. consultant inside at a time to serve as a safety observer.

What the observers saw startled them. The Djiboutians regularly ignored air traffic while listening to music, playing video games, and gabbing and texting on their phones, according to reports that the observers filed each week with the Navy.

Some controllers would abandon the tower to take a cigarette break or to pray, even when aircraft were taking off. Others gave pilots the green light for a landing without looking out the window to make sure the runways were clear.

The late-night shift was the worst, according to the documents. Drowsy controllers would lie down on the job, giving orders to pilots from mattress pads on the floor. On more than one occasion, controllers had to be awoken by a U.S. safety observer after they ignored radio calls from pilots approaching the airport.

Also posing a problem was a lack of modern equipment, including an air traffic radar system. The Djiboutians relied on an aging French air defense radar that was not certified for air traffic. Djiboutian officials said the U.S. military had promised them a new radar but never made good on the commitment.

After monitoring the tower for several months, the U.S. consultants delivered some sobering statistics to the Navy.

When it came to keeping aircraft safely separated in the air, the Djiboutian controllers committed an average of 2,378 errors per 100,000 aircraft operations over a three-month period — a rate 1,700 times the rate in the United States.

That led to numerous close calls in the sky and on runways. In May 2013, a private plane carrying Djibouti President Ismail Omar Guelleh almost collided in midair with a Kenya Airways jet, according to the documents.

One of the U.S. consultants concluded that Djibouti for years had avoided a major aviation disaster “only by the grace of God.”

In an interview, the consultant, who spoke on the condition of anonymity to avoid retaliation, said he could not believe the risks that U.S. military pilots had to put up with.

“My concerns were for those boys and girls flying through there,” he said. “To have that level of safety that was present, I thought was unconscionable.”

Navy Capt. Kevin Bertelsen, the commanding officer at Camp Lemonnier when the consultants arrived, called Djibouti a “challenging environment.” But he said conditions had improved.

“Aviation safety is job one any time the U.S. military is engaged in air operations,” he said. “We take it very, very seriously. We’re talking about our brothers and sisters in arms here. We don’t take that lightly.”

Beyond the errors and distractions, some of the Djiboutian controllers were plagued by short tempers, according to the documents.

One controller “screamed” at a PC-12 spy plane pilot coming in for a landing — an incident that a safety observer called “one of the worst cases of unprofessionalism” he had seen in his career. Another controller became “extremely agitated” with another PC-12 pilot for making a routine request; the plane was forced to circle overhead until the pilot apologized on the radio.

In April 2013, a controller “physically beat” a Djiboutian supervisor and threw him down the steps in a dispute over a tiny sum of money — about $3.30, according to the documents.

The next month, a controller threatened a U.S. Navy officer with a metal pipe and vowed to “slit Americans’ throats” if he ever encountered them away from the base. The incident was reported to the Naval Criminal Investigative Service and Djiboutian authorities, but the controller kept his job, records show.

In June 2013, a Yemenia airlines plane and an Ethio­pian Airlines flight were on a collision course because of an error by an air traffic controller. A U.S. safety observer intervened in time to avert a catastrophe. But the controller “erupted with a cursing tirade” and accused the American consultants of being spies. The observer fled the tower by climbing out on a catwalk.

In an interview, Jeff Griffith, the Washington Consulting Group’s vice president for aviation, declined to criticize the Djiboutians or the Navy. He said the firm did the best it could.

He acknowledged that “there were a couple of controllers that were resistant to us being there.” But he said Djibouti had a more advanced aviation network than some countries in Africa.

“I think the operation overall is safe,” he said. “Yes, it can be improved. If we had a chance to help them again, we’d help them right away.”

In July 2013, the Djiboutians kicked the U.S. consultants out of the tower for good.

In one of their final reports to the Navy before leaving the country, the consultants included a chart. It calculated how much time they spent organizing classes that the Djiboutians failed to attend.

“Hours Wasted,” it read: 2,083.