The strike by Servisair staff disrupted operations at Dublin Airport yesterday, with cargo flights cancelled, others diverted to Belfast, and freight being flown back to Germany after ground staff refused to unload it.
In contrast, passenger services at both Dublin and Cork airports ran smoothly, according to Aer Rianta.
A Lufthansa spokesman said its legal representative was being brought in to deal with the refusal of Aer Lingus staff to unload cargo and mail which were flown in from Frankfurt. Under Lufthansa's arrangement with Aer Lingus, the Irish ground crew normally unload the cargo on to trucks which are then operated by Servisair. However, the Aer Lingus personnel, who are SIPTU members, were instructed by the union not to do any work appropriate to their striking colleagues in Servisair, or to assist people who were doing this work.
On the basis of this instruction they refused to unload the plane, although Servisair had personnel ready to drive the cargo away.
Aer Lingus has a similar arrangement with Alitalia and Sabena airlines and has contacted them to prevent a recurrence of yesterday's situation in the coming days.
Meanwhile, KLM has cancelled its daily cargo flights into Dublin for the duration of the dispute, while a number of smaller British cargo firms have diverted flights to Belfast. British Midland announced last night that it was scaling back its cargo operations to an emergency service until Monday, when it expected a full service to resume.
A Servisair spokesman said strike notice had been served before Christmas and a number of the firm's customers had made alternative arrangements.
The spokesman said the firm remained available for discussions with SIPTU.