Complex sentence: It absolves 2 flights in Aug 1998 and June 1999, each time the balloon was started from the Columbia Scientific Balloon Facility in Palestine, Texas and flies 40.000 metres high for over 8 hours.
Split into simpler sentences: It absolves 2 flights in Aug 1998 and June 1999. For each flight the balloon was started from the Columbia Scientific Balloon Facility in Palestine, Texas and flew to an altitude of 40,000 metres for over 8 hours.