Which Boeing aircraft series was designed as a direct competitor to the Airbus A320?

The Boeing 737 family was designed specifically to compete with the Airbus A320, making it the correct answer. The Boeing 737 is a narrow-body aircraft that primarily serves short to medium-haul routes, similar to the A320 series. Since its introduction, the 737 family has gone through several generations and improvements, such as the Next Generation and 737 MAX variants, to enhance performance and passenger comfort while keeping pace with technological advancements and competition in the single-aisle market.

The other aircraft series mentioned, such as the Boeing 777, 787 Dreamliner, and 747, cater to different market segments. The 777 is a wide-body, long-haul aircraft, while the 787 Dreamliner also targets long-haul travel with advanced aerodynamics and fuel efficiency. The 747, known as the "Jumbo Jet," is a larger wide-body aircraft designed primarily for long-haul international travel, significantly differing from the roles of the 737 family and A320. Therefore, the direct competition between the Boeing 737 and Airbus A320 establishes the 737 family as the appropriate answer.