LONDON , England ( CNN ) -- British Airways is asking thousands of its staff to work for free for up to four weeks , spokeswoman Kirsten Millard said Tuesday . British Airways plans to reduce capacity by 4 percent next winter by parking up to 16 aircraft . In an e-mail to all its staff , the airline offered workers between one and four weeks of unpaid leave -- but with the option to work during this period . British Airways employs just more than 40,000 people in the United Kingdom . Last month , the company posted a record annual loss of £400 million ( $ 656 million ) . Its chief executive declared at the time there were `` absolutely no signs of recovery '' in the industry . `` In 30 years in this business and I 've never seen anything like this . This is by far the biggest crisis the industry has ever faced , '' said Willie Walsh , British Airways ' chief executive . Watch more about BA 's request » . A spokesman for one of Britain 's biggest unions said its workers could not afford to work for free for a month . `` It 's all well and good for Willie Walsh to say he 's prepared to work for free when he earns four times in a month what they do in a year , '' said Ciaran Naidoo , a spokesman for Unite . He pointed out that the airline was not ordering staff to work without pay . `` It 's a request -- you can take unpaid leave or you can work for free , and the chances of people working for free are very unlikely , but there might be some people who want to take unpaid leave . '' Demand for the airline 's passenger seats and cargo holds fell during the last financial year , while its fuel bill rocketed to almost £3 billion ( $ 4.7 billion ) . Walsh said British Airways ' woes were inextricably linked to the downturn in the global economy and that there had been no sign of any `` green shoots '' of recovery . Like its premium-class competitors , British Airways is losing customers to cheaper rivals . The airline 's premium passenger numbers fell 13 percent in the second half of last year , in line with the industry average . Total traffic fell 3.4 percent and while the airline carried 33.1 million passengers last year , it was a drop of 4.3 percent from the previous year . The dip in demand for British Airways ' flights has forced a switch in strategy at the airline . From the end of last year , it has been trying to tempt passengers with lower fares , sacrificing profit per seat for `` bums on seats . '' It plans to reduce capacity by 4 percent next winter by parking up to 16 aircraft . CNN 's Alysen Miller contributed to this report .
Union spokesman : Workers could not afford to work for free for a week . British Airways employs just more than 40,000 people in the United Kingdom . BA 's spokesman : There are ` ` absolutely no signs of recovery '' in the industry . Last year , the company posted a record annual US $ 100 million .