Complex sentence: It was initially delivered to Grand Island Army Airfield, Nebraska as USAAF Serial "45-21768", however once delivered, it was not assigned to any unit until early 1946 when the 46th RS was formed.
Split into simpler sentences: It was initially delivered to Grand Island Army Airfield, Nebraska as USAAF Serial "45-21768". However, once delivered it was not assigned to any unit until early 1946 when the 46th RS was formed.