Complex sentence: In 1972, the A300 made its maiden flight and the first production model, the A300B2 entered service in 1974; though the launch of the A300 was overshadowed by the similarly timed supersonic aircraft Concorde.
Split into simpler sentences: In 1972, the A300 made its maiden flight; its first production model, the A300B2, entered service in 1974. However, the launch of the A300 was largely overshadowed by the similarly timed supersonic aircraft Concorde.