LATAM Airlines Group, parent of TAM and LAN Airlines, has chosen membership in oneworld over Star Alliance for both carriers.

Holding an estimated 40% share of the South American air passenger market, LATAM is making one of the more consequential alliance membership decisions of recent years. Chilean antitrust authorities required LATAM to leave one of the alliances when it approved the merger of Chile’s LAN and Brazil’s TAM in 2011.

LAN is a oneworld member while TAM belongs to Star. TAM will leave Star in the second quarter of 2014, LATAM said in a Thursday statement making the decision official. Signs have pointed to LATAM choosing oneworld for some time.

TAM “plans to officially join oneworld as soon as it leaves Star Alliance,” LATAM said. “From that date, TAM passengers will be able to accumulate kilometers/points by flying on any oneworld member airline. Until then, they will continue to receive the benefits offered by Star Alliance.”

LATAM CEO Enrique Cueto said in a statement, “We evaluated all the existing possibilities and chose the alliance that offers the best benefits to our passengers, in addition to the best connectivity and products, as well as the greater synergies for LATAM Airlines Group. With the incorporation of LATAM Airlines Group to oneworld, passengers flying with us will be able to book trips through the oneworld network of destinations and connect from any of the 950 destinations, including distant and exotic ones such as Hong Kong, Kuala Lumpur, Moscow or Melbourne, through oneworld member airlines.”

Oneworld CEO Bruce Ashby added, “We are delighted that, after its comprehensive review of alliance options, LATAM not only decided to have LAN remain on board oneworld, but also to include TAM and all the other passenger airline subsidiaries in the LATAM group as well. This solidifies oneworld’s long-standing position as the alliance leader in Latin America.”

LATAM carrier LAN Colombia will become a oneworld affiliate member in the 2013 fourth quarter. LAN Argentina, LAN Ecuador and LAN Peru are already oneworld affiliate carriers.

In addition to LAN, current oneworld members are Air Berlin, American Airlines, British Airways, Cathay Pacific Airways, Finnair, Iberia, Japan Airlines, Malaysia Airlines, Qantas, Royal Jordanian and S7 Airlines. In addition to TAM, SriLankan Airlines and Qatar Airways are slated to become new members.

US Airways has already said it will leave Star to join oneworld following the completion of its merger with American.