Could anyone identify the propeller-powered ground-attack planes that lent air support during the South Korean attack in the second half of the movie? Did South Korea not have jet-fighters yet in that stage for the war?
They were U.S. Navy or Marine F4U Corsairs. They were used as fighters in World War II and for ground attack in Korea. The U.S. Navy and Marines had jet fighters but Corsairs were heavily used for close air support in Korea because they could carry heavy loads of bombs and rockets and because their slower speed was, if anything, an advantage in that role. The U.S. Air Force also used propeller-driven fighter bombers for close air support, although Sabre jets were used to fight Communist MiGs in the air.
Pretty sure the South Korean Navy didnt have similar planes because they lacked any aircraft carriers to launch them from. I think the SK air force was pretty obsolete at the beginning of hostilities in 1950. Heck, the US forces werent even in that great shape, the war really jumpstarted US military production and development again.
The main combat aircraft used by the South Korean AF during the conflict was the US-built F-51 Mustang (same as the WWII P-51, USAF terminology had changed from P for pursuit to F for fighter). All F-4U and AU-1 Corsairs in Korea were operated by the US Navy and Marines. The following website includes the most comprehensive list I've found on the net of Korean War aircraft.