The changes will come into effect from the end of November and the airline has reported 1,000 members of cabin crew will take voluntary redundancy and a further 3,000 plan to switch to part-time working.
They will not alter contractual terms and conditions for individual crew members, and will not reduce the number of working crew on board.
A spokeswoman told HR magazine: "British Airways is currently not profitable and we expect to record a significant loss for the second consecutive year - the first time that has happened in our history. Revenues are down, so we must reduce costs to restore profitability."
Thousands of staff across the airline have already made contributions to the cost-reduction programme. In June, almost 7,000 British Airways staff volunteered to take unpaid leave, voluntary pay cuts or work part-time as part of the company's plans to cut costs.
Of the 40,000-strong workforce, 6,940 employees answered British Airways' call to save money and were expected to save the airline £10 million.
But in July more than 2,000 British Airways staff voted to reject proposals from the employer to cut 3,500 jobs and impose a pay freeze to save costs.
The spokeswoman added: "We have extremely professional cabin crew. But we cannot ignore the fact our Heathrow-based cabin crew costs are much higher than those of our Gatwick-based crew and of our competitors.
"We have consulted on these changes and are not altering anything that requires negotiation. Offering high-quality customer service will remain our focus and our most senior cabin crew will become an integral part of the service onboard.
"Without changes, we will lose more money with every month that passes. It is essential we make ourselves more efficient if we are to ensure our long-term survival."
