Wiltshire air ambulance costs up by 15% to £3.75m
Wiltshire's air ambulance says its running costs have risen by about £500,000 to £3.75m, mainly due to training costs for paramedics.
The charity said the increased price of medicines and painkilling drugs also contributed to the 15% rise in costs.
The number of incidents it responded to also rose by 25% over the past year.
Chief executive David Philpott said he hoped the "incredibly generous" people of Wiltshire would raise the money needed.
"The calibre and the training of our paramedics now is quite exceptional," he said.
"They sit in this special place which is more than a... paramedic, but not quite a doctor, and for that they have to do a university course.
"The up-skilling of our crew and the costs that come with that is probably the biggest driver in these increased costs, plus we're busier than we've ever been."
He said the charity had six months of reserves "in the bank".
The charity relies on donations and needs the equivalent of just over £10,000 per day to keep going.
Mr Philpott added he did not know when the service's permanent helicopter would be operational again.
It was withdrawn from service earlier this month due to a mechanical fault.
A backup aircraft is currently being used which can only fly in the daytime.