Mere presence certainly works - both on the ground and in the air.
I have seen the 'suspects' depart at the sight of a uniform lingering on foot on many many occasions and have always held that such subtleties are completely lost on the ranks of ACPO and their like simply because in their headlong rush for money and ranking they actually forgot what real policing is about. You cannot count 'no crime' on your fingers but you can see it - its called tranquility and public safety.
Although I was never a 24/7/365 air support person I was aware of a number of instances where a station has rung in to thank the air unit for their help in getting the suspects to give themselves up .... each time the aircraft was merely in transit to base and was totally unaware of the situation below. If I tripped over a few there must have been many.
Street policing works [when you can get it] and so does air cover [when you can get it].