Complex sentence: However, no NAVs meeting DARPA's original program specification were forthcoming until 2009 when AeroVironment demonstrated a controlled hovering of DARPA's flapping-wing NAV.
Split into simpler sentences: However, no NAVs meeting DARPA's original program specification were forthcoming until 2009. AeroVironment has recently demonstrated a controlled hovering of DARPA's flapping-wing NAV.