The phrase "in sky" can be replaced by several synonyms to add variety and depth to one's writing. One option is "in the heavens," which connotes a spiritual or divine element. "Up above" and "up in the air" are more casual alternatives that suggest a sense of wonder and open possibility. "Aloft" and "airborne" both emphasize the height of the object in question, while "overhead" and "above" convey its positioning in relation to the viewer. Lastly, "flying" and "soaring" both capture the sense of movement and freedom often associated with objects in the sky. Using these synonyms can help make descriptions of the sky more engaging and evocative.