Update 5.40pm: Ryanair has written to trade union Forsa in connection with the airline's cancellation of 16 flights next Tuesday.
In a letter to Forsa's national secretary, Angela Kirk, Ryanair accused the trade union of wasting the airline's time.
"Your letter of today (20 July) arrived after 4pm, some 2 hours after we had cancelled 16 (5%) of our over 290 flights to/from Ireland next Tuesday, unnecessarily disrupting the holiday plans for another 2,500 Irish customers," the letter stated.
"Over the last 2 days - since we met at 3pm on Wednesday - Ryanair has signed 2 recognition agreements with cabin crew unions in German (yesterday) and Italy (today).
"During that same 2 day period, Forsa has none nothing; except hold another pointless strike by a small minority (25%) of Irish pilots today, and refused to call off Tuesday's equally pointless strike which will be ignored by the vast majority (75%) of our Irish based pilots.
"What the last 2 days shows [sic] is that Ryanair is making progress in our negotiations with unions, whereas Forsa are just wasting our time, and disrupting our Irish customers and their families."
Our latest letter to FORSA: pic.twitter.com/rFtfmy9rvh— Ryanair (@Ryanair) July 20, 2018
The announcement comes as 100 pilots based in Ireland and directly employed by Ryanair are today taking strike action with a 24-hour work stoppage.
In a statement today Ryanair said:
"Since FORSA has again failed to answer our call to cancel the 3rd strike by a small minority (25%) of our Irish pilots (who earn between €150,000-€200,000), we regrettably have cancelled just 16 (5%) of over 290 Irish flights next Tues 24 July (only some IRE-UK flights affected).
"All 2,500 affected Irish customers have already been notified by email/SMS and will be readily re-accommodated (or refunded) on other Ryanair flights between IRE-UK routes over the next 7 days.
"It is disgraceful that FORSA sits on its hands for over two days - without any communication since Wednesday - while thousands of Irish customers and their families have their holiday plans disrupted."
— RTÉ News (@rtenews) July 20, 2018
The trade union representing pilots at Ryanair says it cannot rule out further strikes, unless their dispute around seniority is resolved.
It is the second day of strike action by Irish based pilots, with a third set for Tuesday.
Next week around 600 flights are to be downed by a separate cabin crew strike in Belgium, Spain and Portugal.
Niall Shanahan from trade union Forsa says a third party intervention might be what is needed to break the deadlock here: "There's still a lot of work to be done here in that respect.
"As it stands there is no suggestion that there would be a third party involved but certainly in the case of any other industrial dispute that would be a good way to break the logjam."
ATC Update: pic.twitter.com/9VhmdvesXH— Ryanair (@Ryanair) July 20, 2018
Meanwhile, Ryanair have today signed a recognition agreement with the Italian union FIT CISL, who will now join ANPAC and ANPAV as a joint negotiating body for directly employed cabin crew in Italy.
"We are pleased to sign this cabin crew recognition agreement today with FIT CISL in Italy," said Ryanair's Chief People Officer, Eddie Wilson.
"This is a further sign of the progress Ryanair is making with trade unions since our December 2017 decision to recognise unions, with over 66% of our cabin crew now covered by recognition agreements.
"As this growing number of pilot and cabin crew recognition agreements confirms, we are making progress and confounding those sceptics who claimed that our December 2017 decision was not real or genuine.
"We look forward to working closely with both FIT CISL, and their Company Council in negotiating a CLA for our directly employed Italian based cabin crew, and to shortly commence negotiations on a CLA for contractor crew with ANPAC, ANPAV and FIT CISL.”
Today we signed a recognition agreement with the Italian union FIT CISL, who will now join ANPAC and ANPAV as a joint negotiating body for directly employed cabin crew in Italy.
Dublin based Ryanair pilots have moved their picket from the airport roundabout to the company's HQ at Airside in Swords.
It is running from now until 1.30pm today although the work stoppage will continue all day.
4,000 Ryanair customers in Ireland have had their flights cancelled - during their second pilots strike in just over a week.
100 pilots based in Ireland and directly employed by Ryanair say they have been left with no choice but to take to the picket line.
They are members of the Irish Airline Pilots Association and have been represented by the trade union Fórsa during discussions with management.
Unfortunately those talks broke up earlier this week without reaching a deal and with a renewed threat of stoppages during the busy summer schedule.
The first strike day last Thursday was the first in the airline's history.
There is another planned for next Tuesday.
Morning all 🛫July 20, 2018
The second 24-hour strike in a week, by 100 pilots employed by Ryanair in Dublin, is underway.
The pilots, who are employed directly by the company, are striking for 24 hours with another day of action scheduled for next Tuesday.
The pilots, who are members of the Irish Airline Pilots Association, are in dispute with the company over base transfers, leave and seniority issues.
Talks between their union and Ryanair management broke down earlier this week.
With no breakthrough in sight, more strike action is scheduled for next Tuesday.
Last night, Ryanair called on Forsa to call off next week's day of action but a 7 o'clock deadline came and went without any response.
Ryanair calls on FORSA to call off 24 July strike by less than 25% of our Irish pilots (over seniority & base transfer proposals which they can't explain and which don't even affect them): pic.twitter.com/OVse5kmgMi— Ryanair (@Ryanair) July 19, 2018
A total of 24 flights out of Dublin today have been cancelled to the UK.
The company says it is cancelling flights on routes with higher volumes so people can more easily transfer to other services.