A 14-year-old girl died from an asthma attack after an ambulance was directed to the wrong address.
Paramedics were called when Elouise Keeling collapsed with breathing problems during an Air Cadets meeting at an RAF base.
But a call handler is said to have sent the ambulance to another base seven miles away.
By the time a second ambulance arrived at the correct location - 19 minutes after the call was made - crews were unable to save her and she was pronounced dead at the scene.
Elouise's mum Karen Keeling, 33, of Huntingdon, Cambridgeshire, said: "We are totally devastated by Elouise's death. We hope no one ever has to go through pain like this."
Elouise was at an Air Cadets sports day at RAF Brampton on June 25 when she suffered the severe asthma attack despite not having participated in any games.
A senior cadet called 999 at 7.44pm and asked the call handler to send an ambulance. But the crew was wrongly dispatched to RAF Wyton, on the other side of Huntingdon.
When no ambulance arrived, cadet leaders made a second call to 999 and another ambulance was sent to the correct address. Its arrival time of 19 minutes after the first call was more than twice the target time of eight minutes.
The East of England Ambulance Service Trust admitted the delay may have contributed to her death and launched an investigation into whether it was the decisive factor.
Elouise's mother had already reached the base when paramedics arrived and watched in horror as they tried to save her.
Mum Karen said: "We just want justice for our Ellie. She was a bright, happy and healthy young girl who had so much ahead of her and so much of her life to look forward to.
"We hope our daughter's death means that no family has to suffer in this way again."
She added: "They have heard the recording of the call and it was the handler who made the error. They sent it to the wrong place."
Elouise was described by teachers at Hinchingbrooke School as 'a bright, bubbly girl who was very popular, particularly with her tutor group'.
The ambulance service is investigating the death as well as another incident where paramedics arrived late.
John Martin, interim director of clinical quality at the Trust, told its board meeting: "Both of these incidents focus around delays and they are being investigated to find whether this was the specific cause."
An inquest has been opened by the local coroner.