Complex sentence: In 1909 the lake was also the historic site of the first flight of an aircraft in Canada and the British Commonwealth; the airplane, named the Silver Dart, was built by the Aerial Experiment Association under Dr. Bell's tutelage.
Split into simpler sentences: In 1909 the lake was also the historic site of the first flight of an aircraft in Canada and the British Commonwealth. The airplane, named the Silver Dart, was built by the Aerial Experiment Association under Dr. Bell's tutelage.