BBC News Online looks at the unions that lined up against British Airways during the dispute over introduction of a new clocking-on system.
Transport and General Workers Union
This union, known as T&G, represents 2,000 check-in, sales and reservation staff at Heathrow and Gatwick airports, and 28,500 members across BA.
28,500 BA members
2,000 involved in Heathrow and Gatwick disputes
Total UK members: 900,000
Its general secretary, Sir Bill Morris, says the swipecard system itself is not a problem, but workers are worried about how the data it collects could be used.
The T&G has 900,000 members in every type of workplace.
The union was founded in 1922, and is divided into four sectors: food and agriculture, manufacturing, services and transport.
There is also a sector dedicated to women, race and equalities.
The transport sector represents more than 200,000 workers from commercial road transport, docks and waterways and civil air transport as well as all passenger services.
The services sector represents more than 300,000 public service, white collar, construction and general workers.
Sir Bill Morris has been the union's general secretary since 1991.
The GMB represents 11,000 BA staff. 750 of its members are involved in the Heathrow dispute, with a further 350 at Gatwick.
GMB leader Kevin Curran has said nothing will be resolved until BA wins back the confidence of its workers.
11,000 BA members
750 involved at Heathrow, 350 at Gatwick
Total members: 700,000
The GMB wants management to start with a clean slate remove the swipecard entry system from airports.
It says it will then be prepared to enter into negotiations about the system and any future changes BA might be planning - such as the introduction of a network of electronic systems known as Integrated Airport Resource Management (iARM).
It believes iARM would lead to a new rostering arrangement for staff, linked to the swipecard initiative, which would factor in busy and quiet times at airports.
BA has said it has identified the iARM system as a "suitable" way of managing staff as it moves towards modernising its systems over the next five years.
The GMB refers to itself as "Britain's general union" and represents 700,000 people, nearly 40% of whom are women.
It is the sum of a number of mergers of longstanding trades unions representing a number of production and service sectors and trades.
One in every 31 employees in Britain is a member of the GMB, which has more than 25,000 shop stewards.
It has represented workers for the past 112 years, and members recover over £1 million each week in compensation.
Amicus represents 20,000 BA workers, 8,000 of whom work at Heathrow and Gatwick. Up to 400 of these are check-in staff.
20,000 BA members
400 involved at Heathrow and Gatwick
Total members: 1.1 million
The union has said it would call for a cooling-off period, with staff continuing to sign in using the old paper method until an agreement is reached.
It says it is not opposed to the swipecard entry system itself, but is concerned about the way the information it collects might be used.
It is worried the working patterns of its members might be disrupted at short notice, and says it is angry that the system has been introduced without agreement from its members.
Amicus was formed earlier this year when the Amalgamated Engineering and Electrical Union and MSF union merged.
It is both the UK's largest manufacturing union and largest private sector union.
It has 1.1 million members throughout the private and public sectors. Its general secretary is Derek Simpson.
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