Complex sentence: The pilot, who escaped with minor injuries, reportedly took off with little or no aviation fuel aboard although the fuel gauge he was looking at showed full fuel, but it was the "automobile's" fuel gauge, not the aircraft's.
Split into simpler sentences: The pilot, who escaped with minor injuries, reportedly took off with little or no aviation fuel aboard. The fuel gauge he had sighted indicated that the tank was full, it was the "automobile's" fuel gauge, not the aircraft's.