Complex sentence: Throughout 1949 the Air Force public relations machine had been extremely effective, using aviation magazines and other widely circulated press organizations to publish informative articles, garnering support both in Congress and directly with the American people.
Split into simpler sentences: Throughout 1949 the Air Force public relations machine had matured to be extremely effective. Using aviation magazines and other widely circulated press organizations to publish informative articles, garnering support both in Congress and directly with the American people.