The ability of an oni to fly is not a consistent characteristic across all depictions.
In some Japanese folklore, oni are depicted as powerful demons with superhuman strength and ferocity. These oni might possess the ability to fly, often using magical powers or flying implements. For example, the oni Shuten-dōji is known to have flown on a wind-powered carriage.
However, other depictions of oni portray them as earthbound creatures, relying on their physical strength and weapons to achieve their goals. These oni lack the ability to fly, and their presence is usually limited to the physical world.
Ultimately, whether an oni can fly depends on the specific mythology and cultural context in which they are portrayed.