The consortium said it followed "a period of due diligence" since an in-principle agreement was announced in June.
The Global Travel Group business, which represents 285 members, will remain a separate membership proposition within TTNG, alongside the Travel Trust Association (TTA), Worldchoice and Independent Travel Experts (ITE).
TTNG said since the initial announcement the team had hosted several webinars and weekly Zoom calls with Global members "to give them a better understanding of the products and services available to them after the completion of acquisition".
Gary Lewis, chief executive of TTNG, said: “We strongly believe that now is a crucial time for travel businesses to stand together and we believe members of both The Global Travel Group and The Travel Network Group will benefit greatly from the additional scale and opportunities the acquisition brings.
“Our purpose is to inspire, grow and protect our individual travel members, and we’re thrilled to be able to support our existing membership propositions through strengthening our core business, whilst facing the current challenges together.”
John Bevan, chief executive of dnata Travel Group, added: “We’re pleased to have been able to complete this process and wish the very best to The Global Travel Group members in their future as part of The Travel Network Group. We know they’re in great hands.
“I want to thank the entire Global team for their professionalism, hard work and efforts during the sale process and over the years.”
The acquisition takes TTNG’s membership to more than 1,250 businesses across the UK.
