Aer Lingus cabin crew will commence their 24-hour strike over rosters at midnight tonight.
Pickets will be placed on Dublin, Cork and Shannon Airports and the cabin crew will march through Dublin Airport to Aer Lingus headquarters at around 10.30am in the morning to hand in a letter to management outlining their position.
The airline has cancelled most of tomorrow's flights in and out of Dublin, Cork and Shannon, but has added some extra flights to its schedules today and on Saturday.
The additional flights are being operated by hired-in aircraft and crews in order to accommodate as many of the 28,000 disrupted passengers as possible.
Aer Lingus would normally have carried around 40,000 passengers on the Friday of a Bank Holiday weekend.
It is estimated the strike could cost the airline up to €10m, with even more losses if the union schedules further industrial action.
Staff positioned outside Ireland when the strike commences at midnight will operate flights back to Ireland as they cannot legally strike until they touch down here.
While Impact represents the vast majority of the airline's 1200 cabin crew, around 50 belong to SIPTU.
SIPTU says those staff are not in dispute with Aer Lingus and will turn up for work as normal. However, they will not be doing any work normally done by IMPACT members.
The pilots' union IALPA has urged as many of its members as possible to attend the cabin crew march.
Meanwhile, efforts are continuing to arrange a date for a meeting between management and Impact early next week in a bid to resolve the row.
The cabin crew say their current roster is erratic and imposes excessive fatigue on them.
They want the same roster that applies to pilots, which involves working five days on, then three days off.
They say management has refused to sanction a trial of the pilots' roster for cabin crew on short-haul routes.
However, Aer Lingus argues that the pilots' roster cannot be applied to cabin crew without additional cost and inefficiency.
The company has warned that it could lead to the establishment of bases in North America to service transatlantic routes, with the loss of 300 Irish-based cabin crew jobs.