Getting the Air Ambulance out can be for a number of reasons… …availability of vehicular ambulances.
I really hope not, seeing as they receive zero funding for their work from official sources
A couple of years ago a teenager hurt himself on a jump on my local hill, and emergency services were called just before I came upon the accident. A very unfit paramedic came puffing up the hill after a while. (The hill in question is maybe a mile, at most two from the city centre. The accident was lower down, at most 60m of climbing up some stone steps, a 10 minute stroll from the car park.) The paramedic called for fire service help as there weren’t any ambulances available – why would there, 11am on a Sunday morning? 😯 The fire crew arrived, had a chat with the paramedic, had a chat with us, the dozen or so MTBers who were now standing around, and decided to call the air ambulance which eventually arrived and got the boy off the hill about 90 minutes after his accident. Luckily he had only a small amount of damage, nothing that was exacerbated by the lengthy wait.