飞往 is used specifically for air travel. Compare: 开往 (drive/depart for, used for buses/trains), 驶往 (sail/drive toward, formal), 前往 (head to, general and formal).
grammar
The 往 in 飞往 indicates direction. Pattern: 飞往 + destination. Similar directional verbs: 走向 (walk toward), 驶向 (sail/drive toward), 奔向 (rush toward).
