Holidaymakers could experience disruption at Dublin Airport from tomorrow.
Servisair, the main ground handling operation for charter airlines, faces industrial action.
Talks are due at the Labour Relations Commission today.
But the indications are it will be extremely difficult to avert a strike.
SIPTU made a last-minute offer to suspend the strike yesterday if the company agreed to suspend the unilateral introduction of new work practices.
However, the company indicated it was not willing to accept the union offer.
A spokesman said SIPTU had proposed nothing new.
If the strike goes ahead it could spread to Servisair operations in Shannon and Cork.
SIPTU members at those airports have offered support to colleagues in Dublin.
Charter companies which use Servisair include Spanair, Monarch and Airtours.
Transatlantic passengers could also face disruption because Servisair provides ground handling support to Delta, Continental and British Airways.
The company also wants 13 redundancies among the 225-strong workforce.
Union representative Mr Dermot O'Loughlin said: "It makes absolutely no sense at this time of year to let people go.
"This is one of the busiest periods, when excessive overtime will be needed to get through the Christmas holiday."
However, a company spokesman said the Dublin operation needed urgent restructuring.
The key requirement was for separate crews loading passenger flights and cargo to be amalgamated into one flexible working unit.
"The company cannot continue with two separate teams," he said.
"The company wants to bring in the sort of flexibility that is commonplace throughout the industry, including Dublin."
Mr O'Loughlin said other airlines at Dublin used separate teams for cargo and passenger flights because the skills were different.
He said amalgamation of teams also meant members would work six Sundays in every seven.
If today's talks at the Labour Relations Commission fail SIPTU members are expected to report for duty as normal tomorrow.
The company said if they were unwilling to carry out new duties it would be regarded as industrial action.