ABOUT 70,000 Heathrow passengers have been left stranded today after an unofficial strike caused British Airways (BA) to cancel all flights until tonight.

The chaos started when 1,000 BA ground staff walked out in sympathy with 800 sacked workers of caterer Gate Gourmet, which serves the airline's flights.

Yesterday more than 120 grounded BA flights left 40,000 travellers fuming in crowded departure lounges, half of them at Heathrow and the rest elsewhere around the world.

BA said about 4,000 people were put up at hotels, while another 1,600 spent the night at Terminals 1 and 4. Some slept in a huge marquee, where they were given blankets and food.

Inbound flights were diverted to cities as far as Glasgow, Newcastle and Paris.

Nearly 100 of BA's aircraft and 1,000 pilots and cabin crew are in the wrong places around the world, the airline said. It cancelled all flights to and from Heathrow until at least 6pm tonight.

Flights by Qantas, Sri Lankan Airlines, Finnair, GB and British Mediterrranean, which are also served by BA ground staff, have also been affected.

No talks have been scheduled to resolve the deadlock between Gate Gourmet and the Transport and General Workers' Union (TGWU), which represents the sacked catering workers.

In a letter to BA, the union confirmed that the action by the airline's baggage handlers and bus drivers was unofficial. It renounced the strike.

A BA spokesman said the company is now circulating the letter among its staff, urging them to return to work.

BA chief executive Sir Rod Eddington apologized to customers. "It is a huge disappointment to us that we have become embroiled in someone else's dispute."

The clash began on Wednesday afternoon when Gate Gourmet brought in 130 temporary staff after dismissing hundreds of its staff. This prompted an un-balloted strike.

Yesterday a manager sacked the afternoon shift after staff missed a 20-minute deadline to report to work.

Gate Gourmet said the actions of some staff put the jobs of its entire 2,000-strong Heathrow-workforce at risk. It also disrupted the supply of 320 flights that daily rely on the UK's largest airline caterer.

The company have been struggling since the September 11 attacks, loosing £22m last year. Without restructuring, it is expected to lose another £25m this year.

Managing director Eric Born said yesterday's strike came as a "devastating blow" after the caterer has met with the unions "on more than 30 separate occasions" to agree on a restructuring plan.

But the TGWU said the affected workers were mostly Asians, earning around £12,000 a year as catering assistants and just under £16,000 as drivers.

The union accused the company of being "heavy-handed" and said it was taking legal advice over the dismissals.

BA urged passengers flying today not to go to the Heathrow, but to first check the status of their flight. Customers due to travel before midnight on Monday can re-book flights.

Heathrow Airport Authority advised passengers of other airlines to check whether their flights would be delayed.