By Javi West Larrañaga

(Reuters) -Irish airline Ryanair has asked some of its flight attendants in Spain to pay back thousands of euros in raises they have received since last year as part of a union deal later struck down in court, documents seen by Reuters showed.

A judge from Spain's High Court ruled in March that an agreement over salaries between union CCOO and Ryanair last year was not valid after rival union USO contested it in January.

CCOO later reached a limited deal with the company that covered only its own members and not those of USO, which had originally wanted a different agreement and was not part of the deal.

Ryanair in April sent an email to its cabin crews unionised with USO asking them to reimburse the accumulated raise they earned via the agreement and lowering their salaries to the level prior to the 2024 raise unless they switch to CCOO, according to documents seen by Reuters.

The human resource official who signed the letter sent to some of the Spanish employees did not respond to a request for comment. The company's press department also did not respond to a request for comment.

A unionised cabin crew member, who requested anonymity due to fears of reprisals, said the company asked him in April to repay 3,857 euros ($4,337) and cut his monthly salary.

He said his salary depends on the number of hours he flies, but is generally close to the minimum wage in Spain, which stands at 1,184 euros per month.

The employee said he was among dozens who were asked to pay back thousands of euros to the company and that many have already done so. Ryanair and other low-cost airlines have gained huge market shares in the region by charging rock-bottom prices to passengers achieved through bare-bone service and salaries much lower than legacy airlines used to pay.

Workers in Ryanair across Europe have gone on strike a number of times over the past years demanding higher pay and better working conditions.

($1 = 0.8894 euros)

(Reporting by Javi West Larrañaga, editing by Inti Landauro and Jan Harvey)