Complex sentence: AOPA's first political activity was to urge passage of a United States Senate bill that would establish the Civilian Pilot Training Program, which allowed thousands of people to earn their pilot certificates with the aid of a government subsidy.
Split into simpler sentences: AOPA's first political activity was to urge passage of a Senate bill that would establish the Civilian Pilot Training Program. This important piece of legislation allowed thousands of people to earn their pilot certificates under a government subsidy.