verfliegen
to fly by
To pass very quickly, especially in relation to time.
Die Zeit im Urlaub ist wie im Flug verflogen.
The time on vacation flew by.

to fly by / fade away
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to fly by
To pass very quickly, especially in relation to time.
Die Zeit im Urlaub ist wie im Flug verflogen.
The time on vacation flew by.

'Verfliegen' is an inseparable verb made up of the prefix 'ver-' and the verb 'fliegen' (to fly). The prefix 'ver-' indicates here that something disappears or gets lost.
Der Zorn des Vaters war zum Glück schnell wieder verflogen.
Fortunately, the father's anger had quickly faded away again.
The perfect tense of 'verfliegen' is always formed with the auxiliary verb 'sein', because it describes a change or disappearance. So it is 'die Zeit ist verflogen' (the time has flown by), not 'hat verflogen'.
Der schöne Sommertag ist leider viel zu schnell verflogen.
Unfortunately, the beautiful summer day flew by much too quickly.
When talking about time, 'verfliegen' (to fly by) is often combined with 'wie im Flug' (as if in flight) to emphasize speed. Typical subjects are 'die Zeit' (the time), 'die Stunden' (the hours), or 'der Urlaub' (the vacation).
Die drei Wochen Sommerferien sind wie im Flug verflogen.
The three weeks of summer vacation flew by.
The reflexive form 'sich verfliegen' has a very specific meaning: a flying living being or object loses its orientation. This meaning is always reflexive, unlike the other meanings.
Der junge Vogel hat sich im Sturm vom Schwarm getrennt und verflogen.
The young bird got separated from the flock in the storm and lost its way.
to fly
'fliegen' and 'verfliegen' can both express that time passes very quickly. For example, you can say 'Die Zeit fliegt' (time flies) or 'Die Zeit verfliegt' (time flies by). Here, 'fliegen' is a figurative, rather image-based form. 'verfliegen' fits very naturally when you want to emphasize that the time has passed almost unnoticed. Learners can easily confuse the words because they look similar and are close in this meaning. The important point is: for normal movement through the air, use 'fliegen'; for time passing quickly, often use 'verfliegen'.

Der freie Nachmittag verfliegt, wenn wir zusammen kochen und reden.
The free afternoon flies by when we cook and talk together.
Im Urlaub fliegt die Zeit immer viel zu schnell.
On vacation, time always flies by much too quickly.