What major change did American Airlines implement regarding its booking system in 2013?

The significant change that American Airlines implemented in 2013 regarding its booking system was the transition to a new reservation platform known as SABRE. This move was part of a broader strategy to update and optimize their operational capabilities. SABRE, which stands for Semi-Automated Business Research Environment, is a technology platform that allows airlines to manage their operations more efficiently, as well as streamline the booking process for customers.

Transitioning to SABRE can lead to enhanced customer service through improved availability and pricing algorithms, making it easier for customers to find and secure flights. This modernization of the booking system not only supports American Airlines' internal processes but also contributes to a better overall customer experience.

While other choices mention valid concepts related to the airline industry, such as online travel agency integration, elimination of paper tickets, or mobile check-in, these actions did not define the major system change made in 2013. Instead, they represent additional advancements that may have occurred at different times or be part of the airline's overall strategy to enhance operations and customer interactions.