This is one of the handworks which doesn't arise from the bind, and instead is part of the deceptions ([Verfuhren]]). Verfliegen means to "fly away" - just like the departures at an airport. In this case, however, as the opponent moves to parry an attack we quickly change direction with a short sharp movement away from their blade, before cutting back in to another opening. This movement appears throughout the text, for example in the Meyer square - we fly off to other openings in succession.
When to Use Verfliegen
One of the key indicators in using Verfliegen is that the opponent parries/cuts at our blade without presenting an immediate threat. If the opponent counter-attacks simultaneously (with a thrust from a Zornhauw, for example) or keeps their point before our faces, then Verfliegen is more dangerous. This is because while we are flying-away with our blade they could set the point on us Ansetzen or otherwise strike us.