Terms of the deal were not disclosed but Equistone Partners Europe director John Walker said the exit generated a “good return” for investors.
Equistone snapped up ATPI for £73m in 2008 and since then has overseen ATPI’s 2009 acquisition of business travel company Instone for £37m from fellow private equity firm 3i.
ATPI, which sat inside Equistone Fund III, is the latest travel sector exit by the firm following the €1bn sale of Global Blue and €200m exit from travel agent Karavel-Promovacances last year.
ATPI, which provides corporate travel to executives travelling to less accessible locations in the marine and oil sectors, will continue to be led by its chief executive Graham Ramsey.
“I believe that there are significant opportunities ahead in the travel sector and look forward to working with ICG to explore these,” he said.
The Equistone Fund III has Barclays as one of its main co-investors after the firm was spun out of Barclays Private Equity in November 2011, in the wake of its own management buyout.