Aer Lingus union threatens industrial action over pensions DUBLIN (Reuters) - Aer Lingus' (AERL.I) largest trade union is to ballot for industrial action after talks broke down over a shortfall in a staff pension scheme, a union official said on Friday. The pension scheme, which employees at Aer Lingus share with other aviation industry workers, has a deficit of over 700 million euros ($956 million). Aer Lingus says it is not legally obliged to help fund the scheme, but has offered to make a once-off payment of 140 million euros to the scheme, a figure SIPTU says is not sufficient. "We will ballot for industrial action, but there will be no disruption of passenger services over Christmas," said a spokesman for SIPTU, who said the union hoped to force Aer Lingus to "engage properly" in the talks. Aer Lingus said SIPTU pulled out of talks after making "completely unreasonable and unacceptable" demands and that the airline's management were consulting with lawyers about SIPTU's actions. SIPTU threatened industrial action last year over talks about the same pension deficit, but later withdrew the threat and returned to talks. Reporting by Conor Humphries; Editing by Elaine Hardcastle