Complex sentence: At 10:36:11 a.m. CDT, the air traffic controller at Oshkosh cleared Flight 290 to land; the flight crews acknowledgment five seconds later was the last communication with North Central Flight 290.
Split into simpler sentences: At 10:36:11 a.m. CDT, the air traffic controller at Oshkosh cleared Flight 290 to land. The flight crew's acknowledgment five seconds later was the last communication with North Central Flight 290.