Amex GBT has announced American Express will retain its 50% stake in the TMC, with US investor Carlyle Group and Singapore’s sovereign wealth fund GIC buying into the share of the business held by a consortium led by investment management firm Certares.

Amex GBT has declined to disclose details of the transaction. It said the move would allow it to maintain focus on its long-term growth strategy.

The University of California Office of the Chief Investment Officer of the Regents and Kaiser Permanente have also joined the investor group.

Certares founder and senior managing director Greg O’Hara will continue as executive chairman of the GBT board of directors.

“This investment validates the success of the joint venture and underscores the strength of our long-term growth strategy,” said O’Hara.

“We are pleased to continue working with American Express and nearly all of our original investors, as well as welcoming Carlyle, GIC and others to the group.”

Paul Abbott, Amex GBT’s recently appointed chief executive Paul Abbott and GBT’s existing executive management team will continue in their current roles.

“To have the continued support of growth-oriented investors willing to commit capital for long-term value creation is great news for our business, our customers and our people,” said Abbott. “We are poised for the next phase of organic growth and M&A activity.”

The joint venture was established in 2014, cementing Amex GBT’s position as, it claims, the world’s largest TMC with more than 18,000 employees across 140 countries managing in excess of $35 billion corporate travel every year.

Amex GBT last year acquired British TMC and technology provider Hogg Robinson Group.