LONDON (AP) - About a thousand ground staff at Heathrow Airport began a two-day strike Sunday, threatening to cause disruptions to flights on Ghana Airways over 20 other airlines.

Baggage handlers and check-in staff employed by Swissport UK and Swissport Cargo walked out at 4.30am (0430 GMT). Swissport said flights operated by Air China, Cyprus Airways and Kuwait Airways were likely to be among the worst hit.

Swissport also handles ground operations for carriers including Aer Lingus, El Al, Icelandair, Japan Airlines, Malaysia Airlines, Saudi and Swiss International Air Lines. It said it would continue to do the work for those airlines during the strike, although the walkout was likely to cause delays.

The company said that while it had set up contingency plans for the strike, it would be able to carry out less than half of its normal work. Airlines likely to be worst affected were Air China, Cyprus Airways, Ethiopian Airlines, Ghana Airways, Hellas Jet, Kibris (Turkish) Airlines, Kuwait Airways, Middle East Airlines, Qatar Airways and Syrian Arab Airlines.

A Heathrow spokeswoman said eight flights would probably be cancelled Sunday. Others could suffer short delays, she added, saying the problems had been "negligible" so far.

"It's all going very well, Swissport have brought in extra staff as have Aer Lingus and they seem to be coping," she said.

Flights by the affected airlines represent less than 10 per cent of the traffic at Heathrow.

Swissport provides a range of support services including baggage handling, cargo loading, check-in and customer service at Heathrow.

The Transport and General Workers Union said the Swissport workers had not received a pay raise for 18 months. It also accused Swissport management of walking out of negotiations last week.

Swissport said it was facing severe problems and had told the union of its proposals to restructure, "with all that implies in terms of employment." It said the union responded with an "unrealistic" pay demand.

It added that airport staff had already gotten raises of between 9.5 per cent and 17.5 per cent over the past two years.