The pilot of the doomed chartered plane carrying a Brazilian football team told air traffic controllers he had run out of fuel and pleaded desperately for permission to land before crashing into the Andes, a leaked recording of the flight's final minutes has revealed.
In the sometimes chaotic exchange with the air traffic tower, the pilot of the British Aerospace 146 jet requests permission to land because of "fuel problems" without making a formal distress call.
A woman controller explained another plane that had been diverted with mechanical problems was already approaching the runway and had priority, instructing the pilot to wait seven minutes.
As the jet circled in a holding pattern, the pilot grew more desperate. "Complete electrical failure, without fuel," he said in the tense final moments before the plane set off on a four-minute death spiral that ended with it slamming into a mountainside on Monday night.
By then the controller had gauged the seriousness of the situation and told the other plane to abandon its approach to make way for the charter jet, but it was too late.
Just before going silent, the pilot said he was flying at an altitude of 9,000 feet and made a final plea to land - "Vectors, senorita. Landing vectors".
The recording, obtained by Colombian media, appeared to confirm the accounts of a surviving flight attendant and a pilot flying nearby who overheard the frantic exchange. These, along with the lack of an explosion upon impact, point to a rare case of fuel running out as a cause of the crash of the jet, which experts said was flying at its maximum range.
For now, authorities are avoiding singling out any one cause of the crash, which killed all but six of the 77 people on board, including members of Brazil's Chapecoense football team travelling to Medellin for the Copa Sudamericana finals - the culmination of a fairytale season that had electrified football-crazy Brazil.
A full investigation is expected to take months and will review everything from the 17-year-old aircraft's flight and maintenance history to the voice and instruments data in the black boxes recovered on Tuesday at the crash site on a muddy hillside.
The US National Transportation Safety Board was taking part in the investigation because the plane's engines were made by an American manufacturer.
As the probe continued, mourning soccer fans in Medellin and the southern Brazilian town of Chapeco, from where the team hails, held simultaneous stadium tributes to the victims.
The six survivors were recovering in hospitals, with three in critical but stable condition, while forensic specialists worked to identify the victims so they could be transferred to a waiting cargo plane sent by the Brazilian air force to repatriate the bodies.
Alfredo Bocanegra, head of Colombia's aviation agency, said that while evidence initially pointed to an electrical problem, the possibility the crash was caused by lack of fuel had not been ruled out.
Planes need to have enough extra fuel on board to fly at least 30 to 45 minutes to another airport in the case of an emergency, and rarely fly in a straight line because of turbulence or other reasons.
Before being taken offline, the website of LaMia, the Bolivian-based charter company, said the plane's maximum range was 1,600 nautical miles - just under the distance between Medellin and Santa Cruz, Bolivia, where the flight originated carrying close to its full passenger capacity.
"If this is confirmed by the investigators it would be very painful because it stems from negligence," Mr Bocanegra told Caracol Radio on Wednesday when asked whether the plane should not have attempted such a long haul.
One key piece to unlocking the mystery could come from Ximena Sanchez, a Bolivian flight attendant who survived the crash and told rescuers the plane had run out of fuel moments before the crash.
Investigators were expected to interview her at the clinic near Medellin where she is recovering.
"We ran out of fuel. The airplane turned off," rescuer Arquimedes Mejia quoted Ms Sanchez as saying as he pulled her from the wreckage. "That was the only thing she told me."
Investigators also want to speak to Juan Sebastian Upegui, the co-pilot of an Avianca commercial flight who was in contact with air traffic controllers near Medellin's Jose Maria Cordova airport at the time the chartered plane went down.
In a four-minute recording circulated on social media, Mr Upegui described how he heard the flight's pilot request priority to land because he was out of fuel. Growing ever more desperate, the pilot eventually declared a "total electrical failure", Mr Upegui said, before the plane quickly began to lose speed and altitude.
"I remember I was pulling really hard for them, saying, 'Make it, make it, make it, make it'," Mr Upeqgui says in the recording. "Then it stopped. The controller's voice starts to break up and she sounds really sad. We're in the plane and start to cry."
No traces of fuel have been found at the crash site and the plane did not explode on impact - one of the reasons there were six survivors.
However, there could be other explanations. The pilot may have intentionally dumped fuel in the hope of reducing the risk of a fireball in a crash, or the aircraft could have suffered a fuel leak or other unexplained reason for losing fuel.
John Cox, a retired airline pilot and CEO of Florida-based Safety Operating Systems, said the aircraft's amount of fuel deserved a careful look.
"The airplane was being flight-planned right to its maximum. Right there it says that even if everything goes well they are not going to have a large amount of fuel when they arrive," he said.
"I don't understand how they could do the flight non-stop with the fuel requirements that the regulations stipulate."