ATP International has signed a new long-term agreement with technology firm Travelport.
The deal means the travel management company's front-line agents will continue to use Travelport's Galileo or Worldspan booking platforms.
Travelport will also supply technology to ATP's recently acquired marine branch, Instone International.
Graham Ramsey, ATP chief executive, said: "We have a long standing, highly collaborative working relationship with the team at Travelport, who demonstrate strong insight and understanding of our business.
"As we continue to grow internationally, we feel Travelport is a great partner to continue to support our business."
Sandra McLeod, Travelport's senior vice-president for global accounts, said: "Travelport has developed a tailored business strategy for ATPI, to provide solutions that match their international growth strategy.
ATPI continues to grow exponentially despite the ongoing effects of the economic downturn. The partnership between our organisations illustrates our confidence in working together."