Stepdad of Learjet co-pilot, 20, says: 'Our daughter is down there, under the ground with that airplane' as her best friend said audio of final moments 'worst thing I've ever heard'

The friends and family of a 20-year-old pilot who died in a fiery blaze after the jet nose-dived in Florida have spoken out for the first time, with her best friend describing the disturbing air traffic control audio as the 'worst thing I ever heard.' Nathalia Filgueiras died on Sunday after the Learjet she was co-piloting with Jeff Gregory, 55, lost control and nosedived tens of thousands of feet into the ground in West Palm Beach, Florida. The jet exploded into a giant fireball, killing all nine souls on board. It left behind a massive crater in the roadway and a half-mile debris field. Federal authorities are investigating the crash. 'All we know is that our daughter is down there, under the ground with that airplane,' Filgueiras's stepfather, Thiago Corteleti, told The Wall Street Journal. Filgueiras's longtime friend, Mikaela Schluth, told CBS Mornings that she was 'proud' of the 20-year-old, who she has known since middle school. 'She was able to stay calm and give information, up until the last minute,' Schluth told the outlet, regarding the haunting air traffic control audio, which she described as the 'worst thing I've ever heard.' Air traffic controllers in nearby Miami had given the pilots permission to 'deviate left and right' because of 'moderate precipitation... to the southeast.' They described it as 'pretty nasty' as the twin-engine business jet approached the area. Nathalia Filgueiras died on Sunday after the Learjet she was co-operating with Jeff Gregory, 55, lost control and nosedived tens of thousands of feet into the ground in West Palm Beach, Florida The crashed killed all nine souls on board and is being investigated by federal authoritiesThe controllers were then heard describing 'moderate turbulence' before Filgueiras's tone swiftly became panicked as she realized the plane was in trouble.'Seven two two bravo delta, we're descending 8,000... mayday mayday... we're descending 10,000ft per minute,' she said.Seconds later, she screamed: 'Declaring emergency, declaring emergency, we are in an overspeed condition.'Her voice grew even more panicked as she said: 'Descending 20,000ft per minute... we're going to crash into the ground.''I'm here with you, talk to me,' the air traffic controller responded.Filgueiras said: 'We are descending 22,000ft, and we are banking 60 degrees.''We're out of time,' Filgueiras then screamed in a final transmission.The Daily Mail has chosen not to publish the final seconds of audio, which are extremely distressing. Haunting air traffic control audio caught Filgueiras final moments, where she was appeared frightening as she told the controller the plane was rapidly descending. Filgueiras is pictured with her boyfriend Mikaela Schluth told CBS Mornings that she was 'proud' of her friend, but said the audio was the 'worst thing I've ever heard' The pair has been friends since they were in middle school The crash caused a giant fireball and left a crater in the ground where the impact happened Weather conditions in the West Palm Beach area on Sunday afternoon were poor: overcast, with rain and lightning, and winds from the east at 15 mph, gusting to near 25 mph.Harrowing footage showed the Learjet hitting the road at what some experts say was near-supersonic speed.National Transportation Safety Board member Tom Chapman said during a news conference Monday that the aircraft appeared to start breaking up before it made impact and that he expects parts of the plane will be found far away.'We do have some indication that the aircraft was breaking up before impact,' Chapman said. 'We may find parts of the aircraft some distance away from the actual impact site.'The Bahamas-bound jet began its journey at the Austin-Bergstrom International Airport in Texas at 10.37am ET Sunday.The plane was heading east at 35,000 feet when the onboard pilot began reporting problems.Tech tycoon, Adam Robinson, 45, and his 40-year-old wife, Helen Sharp, were aboard the jet with their toddlers, Emma and Charlie, when it crashed. The family of four was traveling from their home in Austin, Texas, to the Bahamas with their nanny, Anita Maria Cetina, and another couple, Rachel Reed and Charmi Fehr, according to a joint statement released by the victims' families. Tech tycoon, Adam Robinson, 45, and his 40-year-old wife, Helen Sharp, were aboard the jet with their toddlers, Emma and Charlie when it crashedThey were traveling with their nanny, Anita Maria Cetina (left), and another couple, Rachael Reed and Charmi Fehr (right)'Adam and Helen were devoted parents, and Emma, four, and Charlie, two, were the light of their lives. Helen and Adam were the love affair that will last forever,' the statement said.'Their warmth, generosity and gift for making people feel welcome touched so many lives. Their loss will be felt deeply by all those who loved them and who they loved in return.'The statement continued: 'Charmi and Rachel were full of joy and adventure. They loved their people fiercely, fully and without hesitation. From the moment they met, they were all in on each other and the life they were building. They are deeply loved, and we will miss them endlessly.'Anita Maria cared for Emma and Charlie with tenderness and devotion, and she was truly part of the family. She showed us a legacy of unconditional love and devotion.'Robinson was an entrepreneur who founded the tech company Retention and regularly gave interviews about building a successful start-up. Gregory (pictured with his wife) was co-piloting the aircraft with the 20-year-old Helen ran a communications firm called Influential PR. She also owned a successful, Aspen-based pottery studio called Helen Sharp Ceramics.'On behalf of friends and family, it is with a heavy heart that we share that our dearest Helen was taken from us too soon,' read a statement from her family.'To know Helen was to love her. The number of people grieving Helen and Adam is a testament to how many people were lucky enough to have them in their lives.'The Palm Beach Post reported earlier on Monday that they had spoken with Helen's father, who said: 'It's quite a blow. We had a daughter, her husband and two grandchildren on the plane.'