The two fixed-wing and one helicopter provided by Life Flight are based at Wellington Airport.
"Not only does it [Kāpiti Coast Airport] provide an alternative to Wellington Airport for our services but also for national retrieval services based in Auckland," they wrote.
"This includes Starship Air Ambulance PICU service which retrieve critically ill children from the greater Wellington region as well as Organ Donation New Zealand and the national ECMO retrieval service based in Auckland City Hospital.
"When Wellington Airport is closed for adverse weather conditions, or for maintenance work, Kāpiti Coast Airport becomes an essential life line to allow us to retrieve critically ill patients.
"If Kāpiti Coast Airport were to close, this would impact upon aeromedical retrieval with potential adverse consequences for patients."
Gurunathan said the medics' warning was "bound to significantly increase" public opposition to any possible closure of flying operations at Kapiti Coast Airport.
"If the new airport owners were not fully aware of the critical services the airport supports when they included the potential closure of the airport as an option, I now put them on notice with the advice that community opposition is increasing."