Complex sentence: The plane, the Ruston Proctor AT from its manufacturer was designed by H P Folland had its first trial on 21 March 1917 at Upavon Central Flying School near Salisbury Plain, attended by 30-40 allied Generals.
Split into simpler sentences: The plane, the Ruston Proctor AT from its manufacturer was designed by H P Folland. It had its first trial on 21 March 1917 at Upavon Central Flying School near Salisbury Plain, attended by 30-40 allied Generals.