Here is what we know about the crash that killed most of the Chapecoense football team, journalists and club dignitaries:
The cause of the crash was, almost certainly, that the plane ran out of fuel. That is supported by the testimony of a flight attendant who survived, the audio recording of conversations between the pilot and the tower, and the fact that the wreckage did not catch fire, and no trace of fuel spillage was found.
It is possible that there was some fuel leak or other malfunction that resulted in the plane running out of fuel. There have also been reports-unconfirmed, and contradicted by the evidence below--that the plane was circling to dump fuel. However, evidence is growing that the plane simply didn't have enough fuel for the flight--or at least, the margin of error was so small that the plane wasn't able to cope with a delay in landing at Medellin.
Several points need to be made here:
(1) Chapecoense originally wanted to fly this charter airline from Brazil to Colombia, with a refueling stop.
That was turned down because only Colombian and Brazilian airline operators are authorized to fly between the two countries. As a result, the travelling party had to fly a commercial flight from Sao Paolo to Santa Cruz de la Sierra, Bolivia. There, they boarded the charter flight for Medellin.
(2) The LaMia plane in question, a BAE Systems Avro RJ85, has a usual range of 1600 nautical miles. It's 1598 nautical miles from Santa Cruz de la Sierra to Medellin. So the plane was at the extreme end of its range--there was no safety margin in the fuel calculations.
(3) When LaMia filed its flight plan from Santa Cruz to Medellin, the person at the airport who reviewed it found a number of problems, the key one being that the flight time and the time that could be flown on the amount of fuel the plane had was the same.
Exactly why the plane was allowed to take off is unclear, but the pilot is reported to have said "there won't be a problem" because "we'll arrive sooner" (i.e. before the fuel runs out).
The same plane had flown between these two cities twice before, and each time had stopped to take on fuel at Cobija, on the Bolivia/Brazil border. That option wasn't open this time, because that airport is closed at night. However, the pilot could have refueled at Bogotá, before proceeding on to Medellín. Why didn't he? And, why did he not declare a fuel emergency sooner than he did? (Initially he reports a "fuel problem", not an "emergency", and never called a Mayday).
Perhaps these stories shed some light on the subject. Infobae, a news service in Argentina, quotes an aviation source (who wishes to remain unnamed) who explains that private and charter pilots often engage in two things that extend the range of the aircraft by saving fuel. First, by flying at high cruising altitudes, the drag on the plane is reduced, so fuel economy is extended. Second, when they descend, they point the nose and draw power to the engines. According to this person, these are common practices. (It should be made clear that commercial airlines have to comply with strict protocols and cannot engage in these sorts of practices).
So, presumably this is what the pilot meant--he figured (probably from past experience flying this plane) that by doing these things, he would be able to land in Medellin without needing a refueling stop. And, he would have--except for something he could not have counted on.
As the Chape flight approached the Medellin airport, it was put in a holding pattern. The reason was an Airbus A320, flying from Bogota to San Andres Island, had declared a fuel emergency (a suspected leak) and had been given priority to land. (This is all explained in more detail here). Infobae quotes the aviation expert again, "what this did (the two circles in the holding pattern) was to use up the fuel he had saved en route--he had to increase the power to engines he had previously operated at lower power, and he was flying at lower altitude, so fuel was consumed more quickly. Maintaining that power was what cost him the most loss of fuel".
When he started to circle, he was only about 3-4 minutes from the airport--he circled for seven minutes while the Airbus landed. There was another plane due to land ahead of him, the controller asked him how much fuel he had left and he said "I'm almost out, I have a fuel emergency". At that point she tried to guide him in to the airport, but he had lost power and crashed into a mountainside 10 miles from the runway.
Tragic as this occurrence was, there is likely a bigger issue here. La Mia was the charter airline (and this was the same plane) that transported the Argentina NT from Buenos Aires to Bela Horizonte and back last month, and has transported numerous other football squads including the Bolivia, Venezuela and Brazil national teams, and other South American clubs in the Copa Sudamericana.
There is plenty of evidence that the airline was pushing the limits of safety when it came to fuel consumption. The same Avro RJ85 made three flights, nonstop, from Medellin to Santa Cruz de la Sierra. Each lasted about four and a half hours, and there was no stop for fuel en route. So presumably, they were landing on fumes--or close to it.
It has also been reported: " A source at Argentina's transport ministry tells FlightGlobal that LAMIA Bolivia, which had operated a flight to Argentina earlier this month (i.e. November) from Brazil, had arrived in Buenos Aires with only 15min of fuel reserves on board." (That is far less than is recommended). Was that the flight from Bela Horizonte? It certainly seems possible. If so.....wow. We're so used to football squads flying charters all over the world; it's stupefying to imagine that supervision over these flights can fail so drastically.
As of today, LaMia's website has been taken offline; the Bolivian authorities have suspended the company's license to fly.