The company reported a loss before tax of £401 million for the year to 31 March, after seeing its results hit by a weak pound and higher expenditure per gallon of fuel.
Willie Walsh, chief executive, indicated that BA would put pressure on its to reduce costs.
"The prolonged nature of the global downturn makes this the harshest trading environment we have ever faced," Walsh told investors.
He said there was "no immediate improvement visible" and the company's executives offered no guidance for the current year due to difficulty forecasting sales.
The airline has announced plans to mitigate against further losses. BA has already cut more than 2,500 jobs since last summer, and announced redundancy-related costs of £78 million.