'We are in an overspeed condition descending 20,000 feet per minute,' the co-pilot yelled, 'We’re going to crash into the ground!' The pilot of the Florida Learjet 60 crash sent out increasingly desperate distress calls moments before the aircraft plunged into a Florida roadway on Sunday, killing all nine people on board. In a chilling final exchange with air traffic controllers, the pilot warned that the aircraft was descending at an extreme speed and cried out, “We’re going to crash into the ground!” CNN reported, citing air traffic control recordings.The aircraft was travelling from Austin, Texas, to the Bahamas when it crashed in Palm Beach County, Florida. Its final radio transmissions captured the crew's desperate attempts to communicate the unfolding emergency.According to the report, the pilot had reported ice accumulating on the aircraft, an outside air temperature of -47 degrees Celsius and moderate turbulence shortly before the plane began its rapid descent. ‘Mayday, mayday’: Pilot reports emergency The distress calls began at around 12.48 pm ET, when the aircraft was flying over Palm Beach County.According to recordings of air traffic control communications captured by LiveATC.net, the pilot initially reported precipitation and requested permission to climb to 37,000 feet. Air traffic control approved the request.However, seconds later, the pilot declared, “Mayday, mayday!”The aircraft had begun descending rapidly. The pilot first reported a descent rate of 8,000 feet per minute, which soon increased to 10,000 feet per minute. ‘We're descending 10,000 feet per minute’ As the situation deteriorated, the pilot informed the Miami Air Route Traffic Control Center about the aircraft's rapidly increasing descent rate.“We’re descending 10,000 feet per minute!” Filgueiras told the control centre.Moments later, the warning became more urgent.“We are in an overspeed condition descending 20,000 feet per minute,” she yelled. “We’re going to crash into the ground!”At 12.49 pm, the pilot reported that the aircraft was falling at 22,000 feet per minute, equivalent to around 367 feet per second.The final transmission came at 12.49.17 pm.“We’re out of time.”Flight-tracking data from ADS-B Exchange showed that the aircraft had plunged around 27,000 feet in approximately one minute before its signal was lost. What happened before the aircraft lost control? CNN reported that the pilot had described icing conditions and moderate turbulence shortly before the emergency.The aircraft was flying at approximately 35,000 feet, where temperatures can be extremely low. The pilot reported an outside air temperature of -47 degrees Celsius and described “light, clear ice that is manageable and moderate turbulence”.The National Transportation Safety Board (NTSB) said weather conditions were a major focus of its investigation.Icing is a serious aviation hazard. According to the Federal Aviation Administration, ice accumulation can increase an aircraft's weight, reduce lift, decrease thrust and increase drag. It can also make controlling the aircraft's speed and flight path more difficult.The NTSB said investigators were also examining evidence that the aircraft may have broken apart before hitting the ground.The cause of the crash remains under investigation. The NTSB is expected to release a preliminary report within 30 days.