bjcc
As you say, none of us was there. However, what we do know is that the both pilots were in fact under the aviation limit which is extremely low - it's effectively zero for all practical purposes.
Given that they were, it is inconceivable that there was alcohol on their breath and, it does seem at least very odd (perhaps unlikely?) that there could have been anything about them which could have caused the PCs who attended to reasonably suspect they had been drinking. And both pilots, at that.
The point would have no force if they were under the road limit (4 times higher) because it's possible to smell of alcohol and yet still be under the road limit.
True, we don't have all the facts from either side. However, you clearly assume, in the absence of facts to the contrary, that the PCs acted reasonably. Why shouldn't others assume in the absence of facts to the contrary, but in the circumstances mentioned above, that they didn't?
I take your point that 'supervisory rank' officers didn't necessarily play any part in what happened. However, in light of what did happen here, even on the bare facts we do know, perhaps there's a good argument that the nature of the 'complaint/report' should be considered by someone of supervisory rank before constables are dispatched to aircraft. It would take only minutes.
eg If a report was from some anonymous caller who claimed the pilots must have been drunk because they sounded 'relaxed', a supervisor could treat the report with such importance as he thought it justified and decide what action, if any, was required.
Whether or not in theory the police should follow up every call they receive, in practice they don't.