Internet services between India and Europe were disrupted after two undersea internet cables in the Mediterranean were damaged.
One UK software company told Computer Weekly that it had taken four hours to send a 3K file to its offices in India.
Network operator Interoute re-established business-critical links within five hours for its Indian clients, including a bank and a large IT outsourcer.
British Airways said it had been aware of the issue and was able to reroute communications and use alternative call centres to alleviate any problems.
Services went down last Wednesday at 2.30pm Indian local time when the cables were damaged. The cause is being investigated, but repairs could take up to 15 days, according to RS Perhar, secretary of the ISP Association of India.
"Two fibre connections carrying internet traffic along the western route towards Europe have been cut. Internet traffic is being rerouted along other fibre connections, but bandwidth will be throttled along these routes to cope with the transfer of traffic," he said.
Perhar added that the main ISPs in India used more than one line connection to serve businesses, but in this case the main and backup lines were near each other, resulting in the downtime.
Heath Jackson, director at Xantus Consulting, advised businesses with outsourced IT that relied on internet connections to India to improve resilience by specifying in their outsourcing contract that main and backup lines be sourced through separate ISPs and cables.