Complex sentence: In 1965 a twin-engined variant of the PC-6 was built as the PC-8 Twin Porter, although it first flew on 15 November 1967 it remained an experimental and one-off type and development was stopped in 1972.
Split into simpler sentences: In 1965 a twin-engined variant of the PC-6 was built as the PC-8 Twin Porter. Although it first flew on 15 November 1967 it remained an experimental and one-off type and development was stopped in 1972.