Ryanair chief executive Michael O'Leary warned last night that pilots who do not retrain to fly the airline's new fleet could lose their jobs in the autumn.

Mr O'Leary made the statement as it emerged that two groups of pilots have turned down the carrier's most recent offer of training for flying the new Boeing 737-800 aircraft, which Ryanair will fully phase in from September.

Almost all of the Ryanair's Irish-based pilots have lodged victimisation claims with the Labour Court against the airline. If all the claims were upheld, it could result in a maximum liability of €52 million for the airline.

The pilots have been told that they must drop the victimisation claims as one of the conditions of the most recent offer. The offer also states that the pilots will have to personally repay the €15,000 cost of their training if they leave within five years or if the airline is forced to deal with a trade union within that time.

The pilots have told the airline in a letter that they believe accepting its offer would "compromise certain statutory rights whilst under the threat of the loss of livelihood and/or a Dublin base". They want guarantees that they will remain in Dublin.

Captain Evan Cullen of the Irish Airline Pilots' Association (Ialpa) said yesterday it was questionable whether the condition on collective bargaining could be enforced. He also said that the pilots were not prepared to drop their victimisation claims.

Ryanair has responded to seven senior Dublin-based pilots, who refused to sign up to the deal on Monday 27th June, with a new offer of a post at its German hub in Hamburg-Lubeck, or any other that the company chooses, after they have finished training. It has yet to make an offer to another group who refused to sign up last Friday.

Yesterday, Mr O'Leary told The Irish Times that Ryanair would continue to offer training to the pilots for as long as possible, but said that they "would eventually run out of road" as the Boeing 737-200 craft that they are currently flying would be phased out in September.

"The 200s are going in September, if you cannot fly the 800s, then you will no longer have a job in this company," he said.

Mr O'Leary added that Ryanair had consistently made offers guaranteeing the pilots a base in Dublin, but had been turned down.

He pointed out that the latest offers made to the pilots were exactly the same as the agreement made with Captain John Goss when he recently settled a recent High Court case against the airline.

Mr O'Leary argued that Ialpa had recommended that Capt Goss sign the agreement.

However, Capt Cullen said last night that that case was "unique" and could not be compared with the situation of the other pilots.