After receiving assurances from the CAA that an Air Operator Certificate would be issued soon, the charity cancelled a contingency arrangement with Specialist Aviation Services for the use of a back-up MD902 helicopter.
But it has been left “extremely frustrated” by the wait for the essential paperwork to come through.
WAA spokeswoman Jill Crooks said: “We are waiting for the CAA to issue the for our Bell 429 helicopter in order for this to return to Helicopter Emergency Medical Service (HEMS) work.
“We took the decision to let the MD 902 go at the start of August given the impending inspection of our flight operations by the CAA, which was successful, and were told the issuance of our own AOC would be imminent.
“In addition, the owners of the MD 902 wanted it for another contract and we had already spent £314,000 on the contingency arrangement.
“Bearing in mind that the flight operations inspections were successfully completed on August 16 and we expected our AOC in the ensuing days, this was clearly a sensible decision. However, since that date we have been left waiting for the certificate.
“We are, of course, extremely frustrated with this situation but continue to respond to medical incidents in our Rapid Response Vehicles (cars).”
The WAA’s helicopter was grounded on January 4 after Heli Charter, the company which held WAA’s flying certificate, ceased trading. It had previously been grounded due to technical problems which were noted on January 2.
Pilots and paramedics are still able to train on the Bell 429 helicopter day and night in preparation for obtaining their own AOC.
But they are not yet allowed to use the air ambulance for a return to HEMS work until the AOC is received.
Mrs Crooks said: “The process to secure our own AOC is ongoing. The AOC will allow our Bell 429 helicopter to return to HEMS work.
“In preparation for securing our AOC our pilots and paramedics are training on our helicopter, which includes flying day and night.
“We remain operational providing critical care in Wiltshire and surrounding counties up to 19 hours a day.
“We are not using a helicopter for HEMS work but our paramedics are using two Rapid Response Vehicles (cars) to attend emergencies.
“These vehicles are equipped with the same specialist medical equipment that is on our helicopter.
“We have reciprocal arrangements with neighbouring air ambulances to respond to emergency incidents.”
The CAA has been approached for comment but none has been received.