The Panama Canal has a limited capacity determined by operational times and cycles of the existing locks and further constrained by the current trend towards larger (close to Panamax-sized) vessels transiting the canal which take more transit time within the locks and navigational channels, and the need for permanent periodical maintenance works due to the aging canal, which forces periodical shutdowns of this waterway. On the other hand, demand is growing due to the rapid growth of international trade. Also many users require a guarantee of certain level of service. Despite the gains which have been made in efficiency, the Panama Canal Authority (ACP) estimated that the canal would reach its maximum sustainable capacity between 2009 and 2012. The long-term solution for the congestion problems is the expansion of the canal through a third set of locks.
The size of ships that can transit the canal, called Panamax, is constrained largely by the size of the locks, which require ships to be less than 115 ft (35.05 m) wide and 1,050 ft (320.04 m) long, and have a draft of less than 41.2 ft (12.56 m) deep. The third set of locks will allow transit of larger, Post-Panamax ships, which have a greater cargo capacity than the current locks are capable of handling.
All of the canal-widening studies since the 1930s have determined that the best way to increase canal capacity and allow the Panamanian maritime route to continue to grow is by building a third set of locks larger than the 1914 locks. The US began excavations for new locks in 1939, but abandoned them in 1942 because of the outbreak of World War II. This conclusion was again reached in the 1980s by the tripartite commission formed by Panama, Japan, and the United States. More recently, the studies developed by the Panama Canal Authority (Spanish: Autoridad del Canal de Panamá (ACP)) for its 2025 master plan confirm that a third, larger set of locks is the most suitable, profitable, and environmentally responsible option.