Complex sentence: The 144th FW started the conversion process to F-15C Eagles from the Montana Air National Guard with the arrival of the first of 21 F-15s on June 18,2013.
Split into simpler sentences: The 144th FW started the conversion process to F-15C Eagles from the Montana Air National Guard in 2013. The first of 21 F-15s arrived on June 18,2013.