Last year Dragonair, in a settlement with its flight attendants' union, agreed to pay cabin crew their basic salary and allowances on public holidays and when they take annual leave.

The airline, a wholly owned subsidiary of Cathay Pacific that manages its staff separately, also agreed to backdate the payments six years - the first local airline to do so.

If Cathay Pacific were to strike a similar deal with the union representing its flight attendants, it could involve millions of dollars in back pay for the company's 7,000 flight attendants.

Those who had worked for the company for the past six years could be entitled to between HK$28,000 and HK$50,000 each, Ms Kwan said.

Unionist Lee Cheuk-yan said the union had sought help from the Labour Department but was told that the department had difficulties collecting evidence to launch a case against Cathay Pacific.

Mr Lee said it was regrettable to see that a major Hong Kong airline lacked commitment to social responsibility.

Allowances are paid to cabin crew based on the number of hours they fly and the destinations.

At Cathay Pacific, allowances made up 10 to 40 per cent of a flight attendant's earnings, according to Ms Kwan.

Allowances made up 66 to 80 per cent of a flight attendant's earnings at British Airways, said Carol Ng Man-yee, chairwoman of that airline's flight attendants' union.

'We don't like to take days off, because we lose our allowances,' Ms Ng said.

A Cathay Pacific spokeswoman said the company was in full compliance with the Employment Ordinance. She declined to say whether it was willing to negotiate with the union.

A British Airways spokeswoman said the company was in talks with the union, but declined to comment further.