Unlike in previous editions, flying models do not land for combat. So yes, their flying movement stays in effect, and could go over a model.
Flyers can't move over the enemy. Distance is measured by closest part of base to closest part of base (if you play as closest part of model substitute base with model part). As soon as you are base to base (even if you are in the air) any further movement would be taking part of your base further away from the nearest enemy base. Same reasoning for why you can't rotate around a base to let more models in. You are already 0.0" from the enemy model so any further movement does not bring you closer to the enemy. You're basically locked in.
I don't actually think those comments were relating to the question/issue at all. Yes. Of course models can't pile in if they are already base to base. No one is questioning that at all. Can flyers (and also non flyers) pile in over enemy models? If they are not in base to base and if they have enough 3" move to do so and if they end closer to the enemy model.
it's not possible. They can fly over enemy's models in their move phase, but during pile in, you just move toward the closest enemy model, and this will bring you in contact with side A. At that point, you don't fly over it because side B seems nicer.
It sounds like you are "flying" your model as if it is moving flat on the 2d surface right into the enemy model. If so then, yes, it would hit the model, be base to base and not be able to appear on the other side... but then it is not flying... right? Don't these models have the "Fly" rule for a reason? They can "fly" over enemy models, not through them, but actually over. It is as if they can make a vertical move in their horizontal move of X for free, go as high as they want during the lateral move, high enough to go over a model.
Id say that yes, it can fly over the model to pile in, as long as it adheres to the rule to end its pile in closer to the nearest enemy model, ie: end a charge at 1/2 inch. pile in over the top of the model to technically end closer to it in base to base. As stated, models in base to base would be unable to perform this though. which i think is a given.
Ok so in that tactic video I posted above the last strategy about Locking a unit in by using the Pile In and over is relating to what were were discussing here. It seems that the rules as they are written right now only restrict moving over bases of other models during the Move phase, not the Combat phase and also... not the Charge phase! Not the Charge phase!? Yes so you can actually Charge In and Over enemy models, providing you have enough movement to do so and of course the first model must end withing 1/2" of the enemy. Can anyone find a rule to negate this because I think this up and over stuff is rubbish that shouldn't exist. I also don't like the Hook tactic from the video link above pulling an enemy unit into combat that was outside of 3" and not in combat. This should not be allowed but... as written... it is allowed.
Flying models can directly fly over the enemy, but non flyers cannot overlap bases during the charge movement, and can bypass you only if there's enough room to pass by your sides.
Where does it say that? As far as I can see and as already stated there is only one place that mentioned models can't overlap other models and that is in the Move Phase, not the Charge phase.
After re-reading rules and FAQs, must be said that "overlap bases" is not illegal, BUT it depends from the rules you're using: if you measure distance form models, by the parts of the model itself (weamons, arms, tails and so on), without considering bases, you can overlap them; if you use the house rule that measures from base to base, you don't overlap bases (FAQ version 1.1, 1st page). that said: Basic rules say: " models cannot be moved across other models" and only "a model that can fly can pass across models as if they were not there". This is referred to the movement phase, but I don't see anything that let me think that you can pass through enemy models during the charge. If anything, FAQ furtherly specify that you cannot even pass through other friendly models, so I don't see how should be simpler to pass through enemy ones. FAQs (page 4) tell that during pile-in you can move around friendly models or obstacles. It is not said that you can move through enemy models. Only because a thing it's not explicitly forbidden by the rules, it doesn't mean that it's legal. We could say that a flyier can pile-in also on the other side, but pile-in is measured by distance (again FAQ, page 4) and when you are in contact, you cannot rotate around the model. It is not explicitly said, but if you must move toward the nearest enemy model, measuring the distance, it's logical that you must pick the shortest available route, you don't move around it. Another important point is that FAQ (1st page) tell explicitly that you must finish ANY move as a single group. so, even with flyers, if an enemy model closes a passage, you cannot charge it placing some models on one side and some on the other side, becaus at that point you are breaking your unit.