An airplane cannot pivot in one space while flying (maybe planes can while taking off or landing but not while flying at speed). Doing so would probably rip them apart (depending on their speed).
For an airplane to turn, or a bird, some forward progress is required while it turns. A rule like only turning 45 degrees for every X squares forward would be sensible. The faster it goes, the larger X is.
Helicopters can rotate much more easily but again, that's only really possible while hovering, not while moving forward at speed. Same rule, 45 degrees for every X squares.
Really, anything with on set of wings (fixed, flapping, rotating) must not be able to turn in place unless it's also capable of hovering. So, perhaps, allowing greater rotation when successfully hovering would be sensible.
Drones with multiple sets of tiltable wings (rotors) have much greater maneuverability and no longer depend on "front" or "forward" while moving at speed. For drones, X could be so small that it's possibly 0.
None of which is in the rules.
But if I had to resolve ambiguity of a rule, I would try to make that rule conform to common sense or real physics. The 45 degree rule doesn't permit nor restrict making multiple turns in a single square. But both common sense and physics tell me what I need to know: only if hovering, not if moving forward.
Applying that to Starfinder, which has rules for hovering, which themselves also connect to rules for flight maneuverability, I can extrapolate some possible common-sense rules to cover this.
Unfortunately, those are all house-rules because Starfinder rules don't do an adequate job of covering all this. Given how many pages this game and all other RPGs devote to moving and positioning and terrain and obstacles and what can and cannot be done during such moves, this seems to be a fairly important topic - not one to be "Oh, well, they covered some of it and each GM should decide on how to play it."
It would be nice if we got better rules for flying. Rules simulate sensible physics for turning and hovering. Rules that allow creatures and machines with innate flying ability to actually fight and use skills sensibly.
For now, we have what's there.