In a major merger that underscores its faith in business travel, American Express Global Business Travel (Amex GBT) is acquiring CWT in a $570 million deal.

Amex GBT is the world’s largest travel management company, with 20,000 global customers and about $2.5 billion in annual revenue from travel, expense, meetings and events software and services. Its longtime rival CWT is expected to generate about $850 million in revenue in 2024, for a combined revenue of more than $3 billion.

In an investor call, Amex GBT CEO Paul Abbott said that “global business travel spend represents a large under-penetrated opportunity of $1.4 trillion in 2024. So we see significant opportunity to continue to drive share gains and growth.”

CWT’s 4,000 clients will help Amex GBT penetrate industries like energy, media, entertainment and sports, life sciences, and defense and government, Abbott said, and grow its reach into small- and medium-sized companies, which make up about 35% of CWT business.

The company noted that CWT clients will gain access to Amex’s professional services, including travel and expense software, meetings and events services, consulting and sustainability solutions.

CWT CEO Patrick Andersen said joining forces with Amex GBT “helps accelerate our vision of a tech-enabled future for business travel, where people and technology combine to deliver an exceptional customer experience.”

This is Amex GBT’s third huge acquisition in five years. It acquired Hogg Robinson Group for $575 million in 2018, and Expedia’s corporate Egencia business in 2021.

CWT is a private company, majority owned by funds affiliated with Redwood Capital Management and Monarch Alternative Capital.