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.
Claire Hoang, who is part of the legal action, said: "I woke up on Monday with no job. I've lost that month's income. I've also had over £700 of expenses I'll never get back," she told the Victoria Derbyshire show.
She said: "Company troubles had been hanging over us - but we always thought they'd be a bailout. We were always given the mantra: 'don't worry about it we'll sort it out'."
'Promises and lies'
David [not his real name] was headhunted into the company over the summer. He hadn't seen his first pay cheque before the company was liquidated.
He had concerns, given chatter about the business going under. But a senior executive at the company met him face-to-face to reassure him, and David joined Thomas Cook as a head of department.
"We were told there was a recapitalisation in the works - and that it was quite simple and always happen. Then last week the message changed. The deal was still a game changer, but there will be a lot of noise in the media and we should ignore it.
"Then on Friday we were told the next 48 hours are critical and the negotiations are in a critical phase. The same day letters went out to people offering them jobs."
One Thomas Cook flight was in the air when the company went into liquidation, only for the crew to land and discover they no longer had jobs.
"Some people say this might not be a lot of money," says Aneil Balgobin, employment lawyer at Simpson Millar.
"But this is 9,000 families losing a breadwinner - £2,000-£3,000 can make a huge difference when someone is job hunting.
"When people do contact us is often when their mates are getting payments - but by then they've missed the boat."
A spokesperson for the Thomas Cook liquidators said: "We will co-operate with the tribunal process during the liquidation."