Baggage handlers at low-cost airline easyJet are being balloted on whether to strike in a dispute over pay.
Cabin crew at the same airline will also next week start voting on strikes, with any action likely to cause disruption to flights.
The Transport and General Workers' Union said it had been trying to negotiate a pay rise since May and added that the company wanted to link any increase to performance.
The T&G also said easyJet was refusing to recognised the union even though baggage handlers and cabin crew wanted it to represent them on issues such as pay.
About 110 baggage handlers represented by the TGWU work at Luton Airport while 300 cabin crew are based at Luton, Gatwick, Liverpool, Edinburgh, Glasgow and Belfast.
The baggage handlers' ballot closes on Monday, while the result of the cabin crew voting is expected a few weeks later.
TGWU regional officer John Street said he expected a yes vote for action by the baggage handlers.
''Our members are supporting our call for strike action in pursuance of a realistic pay offer and to secure an agreement on recognition.''
The company had imposed a 1.3 per cent pay rise on staff while the union was seeking a substantial increase, he said.
An easyJet spokesman said the company had signed a recognition agreement with the trade union Amicus for all its staff, with the exception of pilots and management.
Go, which easyJet formally acquired on August 1, has recognised Amicus for more than four years.
He said by the end of 2002, the two airlines would be operating under a single Air Operators Certificate with staff in the unified company enjoying identical terms and conditions.
''EasyJet feels, therefore, that, in the best interests of all staff, this can only be done by recognising a single union and one that already represents a significant proportion of the staff of the enlarged easyJet."
Ray Webster, easyJet chief executive, said: ''We actively began the process to recognise a union many months ago, as we felt that it was in the best interests of all of our staff.
"In the meantime we have subsequently acquired Go, which has long recognised Amicus.
Rather than creating a two-tier structure, with staff from easyJet represented by one union and those from Go represented by another, we believe that it is in the best interests of all of our staff to be represented by a single union.
"It would simply be counter-productive to have two sets of unions recognising a single body of staff.
"We are a progressive, good employer - it would have been impossible to grow at the level we have if we were not. We have proactively gone out and recognised a union because we think unions have got a very positive role to play in a company like ours.
''We are aware that the T&G is conducting a ballot of 110 of its members at Luton Airport, but we are confident that our people will recognise that their best interests are not served through strike action."
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