The new system will be supplied by IT services company Amadeus, which took over the running of BA's reservation service and departure control system last year. More than 120 airlines already use the Amadeus reservation system and 150,000 travel agency terminals are connected to it.
The airline plans to move to the Unix-based reservation system from its current mainframe-based system by the end of February.
BA is also developing a "new-generation" inventory management system with Amadeus to help it manage the allocation of seats on flights more effectively.
According to Paul Coby, BA's chief information officer, the new systems will be the lifeblood of BA's business. "The reservation, inventory and departure control system are the fundamental building blocks. You can do all the things you want on a modernised platform and interface," he said.
The move comes amid a sweeping two-year review of BA's IT division.
IT managers have been told they need to find about £45m in cost savings over the next 18 months. The savings are thought to represent less than 10% of BA's total IT budget.
The review includes a consolidation of BA's back-office systems. This will largely involve moving systems supported by older IT platforms to more modern ones such as Unix or Windows NT.
"It will probably take between 12 and 18 months to go through," said Coby. "We will all end up on the same technology. We will shut down some things [older platforms or systems] that people did not realise they never needed, to lower the cost base."