The battle between Ryanair and a significant number of its Dublin-based pilots reaches a significant crossroads this week.

The initial tranche of seven senior pilots due to be retrained on the company's new standardised fleet of Boeing 737-800 aircraft have until Friday to indicate in writing their acceptance of the company's terms for providing that training.

The company is demanding that the pilots agree to refund the €15,000 cost of the training programme if they leave the company within five years or if the airline is required to negotiate with unions over that period.

It has also demanded that pilots drop victimisation claims.

If the pilots do not sign, Ryanair chief executive Michael O'Leary has warned there may be no jobs available for them when the updated fleet comes onstream in the autumn.

Sixty-four pilots and the union Impact have filed a writ with the High Court, accusing the company of breaching their constitutional rights by refusing to engage in collective bargaining through a trade union.