Aer Lingus pilots face compulsory redundancies in January if more volunteers do not come forward to avail of the company's early retirement scheme, according to chief executive Mr Willie Walsh.

So far, fewer than five have applied, compared with more than 1,600 other staff who have opted for early retirement or voluntary severance. Mr Walsh, a former Aer Lingus pilot himself, addressed a meeting of pilots at Dublin Airport yesterday.

When some pilots complained they were being offered a poorer redundancy package than other employees and would forfeit a frozen £20,000 (€25,395) pay rise if they left now, Mr Walsh said the company could not offer to pay more.

IMPACT assistant general secretary Mr Michael Landers said later that the union would hold a strike ballot if the company attempted to introduce compulsory redundancies. He said the package would provide a maximum lump sum of £50,000 to pilots, compared with £180,000 if the same severance formula applied to them as other staff.

"Our problem is that our pilots are being offered less favourable terms than anyone else," he said. "Therefore, fewer pilots have offered to avail of the scheme. What does Willie Walsh expect?"

The company's director of corporate affairs, Mr Dan Loughrey, said the bottom line was that the company had 537 pilots, but only 31 aircraft. The industry norm was five crews, or 10 pilots, per aircraft. Even allowing for holidays, training and other requirements, the current figure was too high.

So far, 14 pilots have opted for career breaks and 44 trainee pilots have been laid off. Another 24 senior retired pilots working on short-term contracts will leave on a phased basis by next September. The company needs at least 80 more to leave.

It would take £16 million of the £40 million available for redundancies to meet the IMPACT demand that pilots receive the same terms as other staff.

The pilots' stance "threatens the viability of the survival plan and the future of the company", Mr Loughrey said. Senior captains have basic pay of £95,000, plus allowances.

About half the pilots are in a younger cohort, earning less than half that sum - but they are still by far the highest paid company employees.

Even if the company wanted to pay more redundancy to the pilots, it could see Labour Relations Commission (LRC) proposals which underpin the survival plan unravel. On the other hand, the Aer Lingus unions accepted the LRC plan on the basis of no compulsory redundancies.