I'm not sure if the following applies to larger aircraft but I have observed the effects in light a/c and gliders:
Some things I have flown (high performance gliders, especially) seem to have a 'bistable' effect in terms of the wing performance.
The theory is that at some airspeeds, there exist two stable states for the airflow over the wing. You can be in either state, depending on whether you have speeded up or slowed down to get to it. I have heard aerodynamicists mutter about laminar attachment, separation bubbles and other techno-gabble but the effects are real (in some particular cases).
A sailplane I used to own climbed noticeably better if you approached the optimum thermalling speed from above, rather than below. It had boundary layer control devices over most of the span and I reckoned there was a small range of speeds where there was definitely some hysteresis in the performance polar.
It's similar to 'planing' seacraft, I think. You can motor along just below the 'critical' speed and be using a lot of power. You can then accelerate over the 'step' to get the boat in a lower drag configuration, then slowly reduce the speed to what it was previously, finding much less power is required to do the same job.