The final moments before a medical ambulance plane crashed in Philadelphia Friday night were captured on an air traffic control tower audio ... and it's bone-chilling.

First obtained by Fox News Digital, the frantic audio from Northeast Philadelphia Airport reveals the instant operators realized something catastrophic occurred shortly after the plane took off.

While one operator makes desperate pleas for the Learjet 55 medical ambulance to respond ... another asks "What's going on down there?" A beat later, the first operator responds, "We have a lost aircraft. We’re not exactly sure what happened." He adds, "The field is going to be closed so no inbounds-outbounds."

Federal Aviation Administration confirmed there were six people on the plane, including a pediatric patient. The agency said the plane was heading to Springfield-Branson National Airport in Missouri before jetting back to Tijuana, Mexico.

The doomed medivac jet was transporting a young patient and her mother with 4 crew members aboard ... several videos capture the aircraft plummeting from the night sky and crashing into the ground, turning into a fireball.

An investigation into the crash is ongoing.