U.K. airline British Airways said Friday that its first-half net profit rose 50.6% to 485 million pounds, or 41.2 pence a share, from 322 million pounds, or 27.4 pence a share, a year ago.

Revenue declined 0.8% at 4.46 billion pounds, impacted by currency movements, and the firm said that it's changing its fiscal-year revenue guidance to between 3% and 3.5% due to continued dollar weakness.

However, a weaker U.S. dollar helped the company to contain costs, with fuel costs falling 3.5% in the period. It also said that it now expects fiscal-yeaar costs to decline by 100 million pounds due to the weak dollar, compared to previous guidance for flat costs. The airline said that fuel costs remain a major challenge and sees a fuel bill of more than 2 billion pounds for the year.

British Airways posted an operating margin of 12.5% in the half year, up from 9.8% a year ago, and said that it expects to achieve its 10% fiscal-year operating margin target.