The new batch of cancelled flights could affect up to 400,000 passengers
The UK's aviation regulator has warned that promises by Ryanair should be taken with a "pinch of salt," as it faces action for its handling of mass flight cancellations.
Andrew Haines, the chief executive of the British Civil Aviation Authority (CAA), said he was "furious" with the no-frills carrier - accusing it of appearing to show "disregard for consumers and for the law," only ever meeting its obligations when it reaches the steps of a court of law.
Ryanair is facing "enforcement action" from the CAA for not giving customers accurate information about their rights following hundreds of flight cancellations.
The airline has pledged to fully cooperate with the CAA investigation.
Ryanair announced yesterday it is extending its flight cancellation plan until mid-March next year.
The plan will see 18,000 further services ditched due to a shortage of pilots.
The cancelled flights - between November and March - could affect up to 400,000 passengers.
The move comes after Ryanair announced it was cancelling 2,000 flights over a six-week period due to miscalculated pilot leave.
The CAA has demanded a meeting with the carrier over the cancellations - and may take legal action.
The authority is set to examine whether the airline falsely claimed that it did not have to re-route passengers on other airlines, particularly when there are no other services available.
The authority has also suggested the airline stopped short of providing details about its obligations to refund expenses incurred by passengers as a result of cancellations - such as meals, hotels and transfer costs.
In Ireland, the Commission for Aviation Regulation has said it is fielding up to 300 complaints a week from affected passengers.
Its head Cathy Mannion has reminding passengers whose flights were cancelled with less than two weeks notice, that they are entitled to €250 compensation.
"The onus is on everybody - all these passengers - to make a claim to Ryanair for the compensation in addition to any other claim they may make for care and assistance," she said.
"For example if somebody was out on holidays and their flight got cancelled, Ryanair would be required to pay for the hotel and the food and the transport."
Fianna Fáil's Robert Troy meanwhile has called for Michael O'Leary to appear before the Oireachtas Transport Committee.
He said the airline's CEO should, “outline I suppose what he is doing to ensure that March is the very latest in terms of when this disruption will last and give a commitment that Ryanair will refrain from selling any seats on any flights that potentially could be cancelled.”
The British CAA has said it is taking enforcement action against five big-name airlines for denying compensation for delayed flights after an ongoing investigation.
The authority has warned it could take legal action against Ryanair for breaching consumer protection laws "if necessary."
Andrew Haines, chief executive of the CAA, said: "There are clear laws in place which are intended to assist passengers in the event of a cancellation, helping minimise both the frustration and inconvenience caused by circumstances completely out of their control.
"We have made this crystal clear to Ryanair, who are well aware of their legal obligations, which includes how and when they should re-route passengers, along with the level of information it provides its passengers."
"The information Ryanair published today again fails to makes this clear.
"In expediting our enforcement action, we are seeking to ensure that Ryanair's customers will receive the correct and necessary information, to make an informed choice about an alternative flight."
On Wednesday Ryanair said it was suspending 34 routes for the winter season from November to March 2018.
Several routes popular with British travellers will be hit, including London Stansted to Edinburgh and Glasgow, Gatwick to Belfast, Newcastle to Faro, and Glasgow to Las Palmas.
Anger against Ryanair has mounted after it came under heavy fire when it recently shelved up to 50 flights every day for six weeks.
Michael O'Leary, the airline's boss, has blamed the move on mismanagement of pilots' annual leave which led over-allocation of blocks of holidays.
The carrier said the latest step will "eliminate all risk of further flight cancellations" as well as remove the risk of similar problems happening again next year.
Mr O'Leary said in a statement: "We sincerely apologise to those customers who have been affected by last week's flight cancellations or these sensible schedule changes announced today."
It also plans to introduce a series of low-fare seat sales for winter 2017 as it is "confident that there will be no further roster-related cancellations."
The company argued less than 1% of the 50 million customers Ryanair will carry this winter are impacted and all affected passengers have received an email alerting them and offering alternative flights or full refunds.
They have also received a €40 travel voucher.
The flight cancellations have so far cost the airline around €24m.
Other airlines facing CAA action for not paying passengers compensation for delays include American Airlines, Emirates, Etihad, Singapore Airlines and Turkish Airlines.