When we talk about the past tense of "fly," we use "flew" to indicate an action that happened in the past. For example, "She flew to Paris last week."
On the other hand, the past participle "flown" is used with auxiliary verbs like "have" or "had" to form different tenses. For instance, "He has flown in a helicopter before" or "They had flown to New York for vacation."
In summary, "flew" is the simple past tense of "fly," used to describe a single past event. "Flown" is the past participle, used with auxiliary verbs to convey different verb tenses.