About 20 airlines are affected by the baggage handlers' strike

Hundreds of members of the Transport and General Workers Union (TGWU) walked out at 0430 GMT on Sunday in a dispute over pay which is expected to hit up to 20 airlines.

Baggage handlers and check-in staff, who are employed by two companies run by Swissport, claim they have not been given an increase in salary for 18 months.

As the 48-hour industrial action began, there were no signs of lengthy queues or stranded travellers.

"The airlines have known about the strike action in advance so they have been in a position to tell passengers and get them rebooked or whatever their contingency plan is," an airport spokeswoman said.

What they are trying to do is cut our terms and conditions so when the aviation market does grow, as it will do inevitably, then they are going to reap the rewards of that Brendan Gold, from TGWU

Flights by the 20 airlines served by Swissport represent only 10% of flights out of Heathrow, the spokeswoman added.

Terminals one, two and three and the cargo terminal at the west London airport are affected.

Talks were held on Wednesday between union officials and Swissport, but it was claimed the company walked out after almost four hours.

Swissport said the union is holding out for an unreasonable pay rise - without paying heed to the problems currently facing the aviation industry.

It added that over the last two years pay had risen between 9.5% and 17.5% and the union was now demanding an increase of 16% which was "totally unrealistic".

'Want to talk'

Brendan Gold, from TGWU, told BBC London: "We understand the problems of the business because we negotiate across the airports in the UK.

"This company do not seem to want to talk to us at all and they are not a bit player. Their group is a big deal and Heathrow is the major international airport. They are here for the long term.

"What they are trying to do is cut our terms and conditions so when the aviation market does grow, as it will do inevitably, then they are going to reap the rewards of that."

Swissport UK said it was not handling the following airlines during the strike: Air China, Cyprus Airways, Ethiopian Airlines, Ghana Airways, Hellas Jet, Kibris (Turkish) Airlines, Kuwait Airways, Middle East Airlines, Qatar Airways and Syrian Arab Airlines.

But it was handling: Aer Lingus, El Al, Icelandair, Japan Airlines, Malaysia Airlines, Saudi and Swiss International Air Lines.