A strike by British Airways cabin crew will ground flights affecting at least 100,000 people next week, despite an emergency plan that should get most passengers to their destination, the company's figures showed yesterday.

Revealing its strike-breaking contingency measures, BA said it would operate all flights from Gatwick and London City airports and more than half of its services from Heathrow during the five-day stoppage, but declined to say what would happen at other airports.

Thousands of BA cabin crew are expected not to turn up for work between Tuesday and Saturday in protest at the imposition of new contracts.

BA said it expected to fly more than 60,000 passengers per day, 300,000 over the dispute – 70 per cent of its bookings. It will attempt to book some of the 100,000 passengers unable to fly on to 50 other airlines with which it has made special arrangements.

The airline's chief executive, Willie Walsh, accused leaders of the Unite trade union of "deliberately targeting" the busy half-term holidays to cause as much disruption as possible to families. "We are confident that many crew will ignore Unite's pointless strike call and support the efforts of the airline to keep our customers flying," he said.

BA has set up a telephone hotline on 0800 727 800 for passengers wishing to rebook.

Unite, which has called four five-day strikes from 18 May, 24 May, 30 May and 5 June, warned next week's stoppage would cause "massive disruption". It claimed 75 per cent of the 10,500 BA cabin crew staff which are members of the union walked out last time and it expects a similar turnout this time.

The dispute has become increasingly bitter. BA has withdrawn its voluntary travel benefits from any employees that walked out in March. According to the union, the airline has also suspended 50 staff and sacked a further seven for "ultimately trivial reasons", including remarks made about the company on social networking websites and allegedly overheard conversations.

The strike is being portrayed as a battle for the future of BA, with the union saying its reputation for service will be undermined by the hiring of cheaper staff and worse conditions for those that remain. BA says cost-cutting measures are necessary to ensure the long-term survival of the airline, which is being undercut by no-frills carriers.

BA lost around £10m a day during the last industrial action and has since lost tens of millions of pounds during last month's volcanic ash disruption.

Last night Unite called on the airline to consider the financial implications of its strike action and to devote that money towards stopping the dispute instead. While not disputing BA's estimate that most passengers will fly, spokesman Andrew Murray said: "The last strikes caused massive disruption. These strikes will cause massive disruption and if they do have services operating it will be at very considerable extra expense. If they want to spend money on various forms of strike-breaking it will hit them on the bottom line. They would be better off negotiating."

Mr Walsh, who apologised to customers likely to be delayed, said: "Our offer is very fair. It addresses all the concerns Unite has raised during 15 months of negotiations and Unite knows we have compromised many times in an effort to get a resolution. This strike action is entirely disproportionate. We remain absolutely determined to resolve the dispute and our door remains open to Unite, day or night."

Speaking on his first day in office, the new Transport Secretary, Philip Hammond, said: "The strikes are going to be very self-defeating and I would urge the union and the management to get around the table as soon as possible."