They are promised an exciting career and the chance to see "the world's top sights", but some who pay the best part of £2,000 for training courses to join a company that supplies Ryanair with cabin crew end up disappointed.

Those who are rejected during their probationary period are still pursued for training costs, while others with jobs are left angry by the working conditions dictated by their contract. Now several have raised their concerns with third parties who have discussed their situation with the Observer.

The trainees are too frightened to speak directly to newspapers for fear that they may be pursued by lawyers for breaching their contracts, which they believe forbid them from talking to the media. But their decision to break their silence will focus further attention on Ryanair after its chief executive, Michael O'Leary, promised to reform its "abrupt culture" and rein in its "macho" image.

Many Ryanair cabin crew are supplied by an Irish firm, Crewlink, which takes them on only after they have successfully completed a six-week training course.

Crewlink runs its own course, but it also accepts recruits from a training school run by St James Management Services, based in Cirencester, Gloucestershire. Those on the St James course pay £1,650 upfront, or £1,800 in instalments. Once the recruit starts working for Ryanair, Crewlink, their employer, deducts £150 a month from their salary to cover the cost of the course if they chose to pay in instalments. But it has been claimed that many who go on the course are rejected during a probationary period, leaving them with a hefty training bill. A Crewlink spokesman said: "The overwhelming majority, over 95%, remain in our employment after six months."

Emails seen by the Observer reveal that St James routinely tells trainees it will instruct a debt-collecting agency to pursue those with outstanding fees. According to the agreement, "successful participants must achieve an 85% or 90% pass rate in all their examinations throughout the course".

Crewlink's contract, seen by the Observer, is clear there is no guarantee of a Ryanair job. Those taken on by Crewlink are paid £13.39 an hour in-flight pay, according to the contract that explains that staff can transferred from one Ryanair base to another "without compensation". In one contract seen by the Observer, the probationary period lasts for 12 months.

The contract also explains that cabin crew are required to work a number of standby days each month whereby they must be available within one hour of being called. Crewlink's contract makes clear that there are no company provisions for sick pay and cabin crew must pay £30 a month for their uniform for the first 12 months. "The company can terminate your employment at any time by giving you the statutory period of notice," the contract dictates. It explains that "there is no notice period for those who have worked up to four weeks".

O'Leary won plaudits last week when he took to Twitter to answer questions from Ryanair passengers, many of whom subjected him to personal abuse. But in a sign that the company is keen to change its image, he promised to listen more to customers. However, he has said little so far about whether he sees any need to change the culture for those who wear the Ryanair uniform.

A Crewlink spokesman declined to comment on "inaccurate claims" about its contract. He added: "If people don't like our terms and conditions, they are free to leave at any time."

Gillian Guy, chief executive of Citizens Advice, said it was concerned that many companies were asking their trainees to pay too much towards the cost of their training.

"Our advisers are increasingly seeing cases, in different sectors, where people are being charged for training, uniforms and travel with the promise of a job that never materialises," Guy said.

A Ryanair spokesman said: "Once cabin crew start working for Ryanair, we pay for all their recurrent training, which is exactly what other airlines do."

Requests for a comment from St James went unanswered.