Complex sentence: MacCready's team built two Albatrosses; the back-up plane was jointly tested as part of the NASA Langley/Dryden flight research program in 1980 and was also flown inside the Houston Astrodome, the first ever controlled indoor flight by a human-powered aircraft.
Split into simpler sentences: MacCready's team built two Albatrosses; the back-up plane was jointly tested as part of the NASA Langley/Dryden flight research program in 1980. The back-up craft was also flown inside the Houston Astrodome, the first ever controlled indoor flight by a human-powered aircraft.