It is one of the most perilous air routes in the world. Colombian pilots must fly through storms in decrepit planes over dense forests to deliver food and goods to villagers isolated from the rest of the world.
Their starting off point is Villavicencio, a city in the foothills of the Andean Cordillera. Their destination is any one of the number of native Indian villages scattered throughout the jungle, cut off from civilisation. Their aircraft are DC3s - the stuff of legends.
First built more than 70 years ago, there are still about 100 DC3s that fly regularly. They have survived war and old age, but of the 30 that remain operational in Colombia half are grounded at any one time for repairs.
Captain Raul does not know the exact age of the plane he flies.
"During the war the flight data wasn't recorded. It only began when we started taking passengers and freight, when civil aviation began," he says. "I think it was updated in 1962."
But the DC3s are one of the few models capable of dealing with the conditions over the Amazon Rainforest - a green hell that poses a danger far greater than storms or mechanical faults.
There is no space for emergency landings in the impenetrable rainforest, which is twice the size of Texas. That is the pilots' greatest fear. Several planes have vanished into the dense jungle, swallowed up by the vegetation.
"It's dangerous. The slightest problem and the plane will just fall out of the sky," Captain Raul says.
Jose is one of the mechanics working on the Flight 1149 aircraft - the only plane with two on board mechanics.
Eighteen months earlier, he was on the same plane when it was forced to make an emergency landing in a rice field 5km from Villavicencio.
"The left engine's cylinder had a problem. It spluttered and then just stopped. We had cargo and 15 passengers on board. We opened the emergency exit and threw out all the cargo. Then the other engine shut down, the pilot decided to try landing in a [paddy] field," Jose says.
"We landed okay, but the propellers were destroyed and the undercarriage was ripped off … but we survived."
For the people of places like Acaricuara, a small Indian village, the arrival of one of the planes is a major event. They stop there only once or twice a month, with a cargo featuring vegetables, beds, dogs, chickens and television sets.
There is no control tower in Acaricuara so everything must be done the old-fashioned way - on intuition, judgement and experience.
And what passes for a runway - a slippery landing zone pitted with holes - is far too short so pilots must be able to land virtually where the runway begins.
Without the DC3, the 100 or so people who live in Acaricuara would be completely isolated.
But Captain Raul never spends more than 15 minutes on the ground there - just long enough to unload. He is particularly keen to steer clear of the crowds of children who gather round and get in the way during takeoff.
"Kids don't realise the danger. They run around playing on the landing strip," he says. "I have to take great care when they scatter around the plane."
'When it's full, off we go'
For Captain Raul and his co-pilot Maria stormy weather can pose one of their greatest challenges - particularly as they do not get paid if they do not fly.
"If we don't fly we don't get any wages. So the more we are airborne the better. We don't get a penny for just sitting around," says Captain Raul.
He is paid far less than a regular airline pilot even though he is responsible for organising the flight and finding his passengers.
"Flights are ad-hoc. There's no real flight schedule with departure times on any given day," he says. "We need to get enough cargo or passengers and when it's full, off we go."
This means, he often decides to fly in highly unpredictable weather - even when pouring rain may have penetrated the petrol tanks, something that could cause the engines to shut down in mid-flight.
He must also make sure that the plane is carrying no more than 1.5 tonnes.
"We have to watch the weight of the cargo, because if something breaks down, we'll have enough time to keep flying to be able to jettison any superfluous loads, so we can complete the flight," he says.
With fuel kept to a minimum, each extra kilo counts. Too much fuel and the plane will be too heavy to take off. Too little could mean crashing into the Amazon.
'It's always nerve-wracking'
Miraflores is a small town in the middle of the Colombian jungle. Until recently, it was notorious for being a drugs capital, under the control of cocaine traffickers and FARC (Revolutionary Armed Forces of Colombia) rebels.
The landing strip - one of the most dangerous in Colombia - is its main thoroughfare.
"Everything has to be worked out, approach speed, the precise place where the wheels must touch down," Captain Raul explains.
"[If something goes wrong], we'll crash or spin off the runway … next to which is a ravine."
The ravine at the end of Miraflores' runway is 80 metres deep and for a plane with 1,800 litres of highly-combustible fuel on board, one short circuit or violent bump could blow everything up.
"It's always nerve-wracking, especially the landings," says Maria. "When I see we're running out of airstrip and the brakes are on full and we start to slide left and right. It just keeps going, there's nothing we can do about it."
But for the foreseeable future at least, Colombia's ancient fleet of DC3s seem likely to keep flying.