Over 1,000 Thomas Cook staff will take legal action after losing their jobs when the airline collapsed.
At an event in Manchester on Friday, around 1,000 former employees came to sign up to legal action under the Protective Award, which is being co-ordinated by union Unite.
More unionised ex-workers are expected to sign up next week at events around the airline’s other UK hubs.
The firm’s liquidators said they will co-operate with any tribunal process.
The Unite-represented employees join around 100 non-union staff who earlier today said they will take legal action.
Both groups argue the airline and tour company acted unlawfully by not offering a Protective Award, a form of compensation given to staff of larger companies who are made redundant without being properly informed or consulted with.
Like the Unite-affiliated staff, the non-unionised Thomas Cook employees believe the firm acted unlawfully in the way they were dismissed and have appointed lawyers to seek redress through an employment tribunal.
Unite was meeting with former staff in Manchester to also inform members of their rights, how to begin redundancy claims with the government and to advise laid-off workers on job opportunities and updating their CV.
The union said it was calling on other airlines currently recruiting staff to “fast-track” the job applications of former Thomas Cook workers.
One ex-senior manager told the BBC’s Victoria Derbyshire programme Thomas Cook was still offering jobs just days before going bust.
Lawyers from one firm, Simpson Millar, told the BBC that thousands of former workers at the firm could be due some money.
Employees are entitled to a Protective Award if they are made redundant from an office of more than 20 people without being properly informed – and are entitled to up to 90 days’ pay.