LONDON: British Airways (BA) cabin crew entered the second day of a four-day strike Sunday, forcing cancellations and bringing disruption for travellers amid no sign of an end to the bitter dispute.

The Unite trade union, which represents cabin crew, is staging its second walkout in a week and says that there is likely to be more ahead unless BA makes them an acceptable offer.

"Until such time as a sensible proposal comes on the table, this dispute will continue," Unite's Steve Turner told the BBC Saturday.

"There are no talks that are scheduled right now. We're willing and available to discuss matters with the company at any point in order to reach a sensible, negotiated, acceptable agreement on behalf of our members."

The strikes centre on what the union says is BA chief executive Willie Walsh's "slash and burn strategy" to cut costs which it claims would lead to a two-tier workforce and damage standards of customer service.

But Walsh has warned the airline could fold in a decade unless the changes he wants are carried out.

"We are trying to transform the way we operate because the industry is changing and the economic conditions have changed so radically that we've got to change," he told the Daily Telegraph Saturday.

"We're doing this to make sure BA still exists in 10 years. If we don't do this, BA won't exist in 10 years."

The latest wave of strikes follows three days of action from March 20 which came the day after talks between the two sides broke down.

BA says it will fly more than 75 percent of customers booked to travel during the disrupted period.

A BA spokeswoman said Saturday that London's Gatwick and City airports were operating as normal and enough staff had turned up to the airline's main hub at London Heathrow to crew the revised timetable.

Walsh visited Heathrow's Terminal 5 to talk to passengers who had their travel plans disrupted and said he found customers "very positive".

"At the same time, I am deeply sorry for those customers who have had their holidays and their plans disrupted," he said in a video message.

Unite claims six Heathrow flights were loaded with passengers then unloaded because of lack of crew and that many long-haul services were leaving 30 percent below capacity. This is denied by the airline.

Some passengers caught up in the strike voiced frustration at Heathrow.

John Cawley and his family were heading to Newark in the United States ahead of a Caribbean cruise but had to hire a minibus to get to Heathrow from Manchester, northwest England, after their internal flight was cancelled.

"It seems there are no certainties with BA at all," he said. "We're having to take this trip one step at a time, once one bit is over we start to worry about the next one. There are question marks over everything."

Outside Heathrow, striking cabin crew set up picket lines and were joined by staff from Iberia, the Spanish airline which is in talks to merge with BA.

The union has claimed the cost to the airline of the strike action would be 100 million pounds (111 million euros, 149 million dollars).

By contrast, BA has said that last week's walkout would cost seven million pounds a day and that an assessment of the cost of the full seven-day action could only be made after it was finished.

BA said last month it expected to notch up a record loss in the current financial year due to weak demand for air travel.

Walsh has also denied accusations that he was trying to break the union, after the claim was made in a letter from 116 industrial relations experts from universities across Britain, published in The Guardian on Friday.

Prime Minister Gordon Brown has condemned the strike but, just weeks before a general election, faces accusations of a weak response from the main opposition Conservatives because Unite is a major donor to his Labour party.