Complex sentence: Of the 266 lost A- 1s, five were shot down by surface-to-air missiles (SAMs), and three were shot down in air to air combat; two by North Vietnamese MiG-17s.
Split into simpler sentences: Of the 266 lost A- 1s, five were shot down by surface-to-air missiles (SAMs). Three Skyraiders were lost in air to air combat, two of them shot down by North Vietnamese MiG-17s.