Ryanair passengers have been dealt a fresh blow after the budget airline announced it will cancel a further 18,000 flights between November and March.

The move will affect approximately 400,000 passengers, who have already been notified via email about the disruption and have been offered the choice of picking an alternative flight or to apply for a refund instead.

Those affected will also receive a £80 voucher - £40 for one-way flights - which can be used to book a Ryanair flight during October for travel between October and March 2018.

"We sincerely apologise to those customers who have been affected by last week's flight cancellations, or these sensible schedule changes announced today," said group chief executive Michael O'Leary.

"While over 99% of our 129 million customers will not have been affected by any cancellations or disruptions, we deeply regret any doubt we caused existing customers last week about Ryanair's reliability, or the risk of further cancellations."

The Irish airline said 34 routes will be affected by the temporary winter suspension, including London Stansted to Glasgow and Edinburgh, London Gatwick to Belfast, Newcastle to Faro, and Glasgow to Las Palmas.

The news comes two weeks after a shortage of pilots forced the carrier to cancel between 40 to 50 flights a day until 31 October, affecting approximately 400,000 passengers across 2,000 flights.

The issue stemmed from Ryanair's decision to shift its holiday year to run from January to December, rather than the current system, which sees it run from April to March. As a result, it had to allocate annual leave to pilots in September and October.

That, coupled with weather delays and air traffic control strikes, left the airline with no other option than cancelling 2% of its flights up until the end of next month and forced O'Leary to admit the airline had "messed up".

Ryanair added it will fly 25 less aircraft of its 400-strong fleet between November and March and then fly 10 fewer aircraft from April 2018. By reducing its flying schedule, the Dublin-based carrier said it will eliminate all risk of further flight cancellations, because slower growth will create "lots of spare aircraft and crews" across Ryanair's 86 bases this winter.

Following the latest round of cancellations, the airline also expects to be able to roster all of the extra pilot leave necessary between October and December before introducing a new calendar leave from the beginning of next year.

"From today, there will be no more rostering related flight cancellations this winter or in summer 2018," O'Leary added.

"Slower growth this winter, will create lots of spare aircraft and crews which will allow us to manage the exceptional volumes of annual leave we committed to delivering in the nine months to December 2017.

"We will start a new 12 month leave period on the 1 January 2018 in full compliance with EU regulations and the Irish Aviation Authority's requirements."

Ryanair added the revised growth plans will translate in full-year traffic rising to 129 million, instead of the expected 131 million, which would nevertheless represent a 7.5% year-on-year increase.

Meanwhile, the Dublin-based carrier also confirmed it had pulled the plug on negotiations with its Italian counterpart Alitalia. In July, Ryanair launched a bid for its stricken rival, as it sought to strengthen its market dominance in Italy even further, but the recent developments have convinced it to pull end talks prematurely.

"In order to focus on repairing this rostering problem this winter, Ryanair will eliminate all management distractions starting with its interest in Alitalia," it said.