Complex sentence: The flights were longest non-stop air route of any airline, over 3500 nautical miles (6,480km, 4,020mi) across the Indian Ocean navigating without the aid of radio the crews relied solely on rudamentary navigation by compass and stars during the trip.
Split into simpler sentences: The flights were the longest non-stop air route of any airline, over 3,500 nautical miles (6,480km, 4,020mi) across the Indian Ocean. Navigating without the aid of radio, the crews relied solely on rudamentary navigation by compass and stars during the trip.