The company has apologised for any disruption caused and says all affected passengers have been contacted.
Andrew Haines, the CAA's chief executive, said Ryanair had been fully aware of its legal obligations and there are clear laws in place to deal with cancellations.
The statement concludes by saying that the "the CAA may seek legal undertakings from operators to ensure they change their policies and comply with the law".
Last evening, Ryanair had announced that it would be suspending 34 routes, including all flights from London to Scotland, all through November to March 2018 as it aims to bring an end to its flight cancellation troubles.
The airline initially blamed a rota mistake, leading to a shortage of available pilots.
The CAA said in a statement that after both sets of cancellations, Ryanair failed to provide customers with "necessary and accurate" information about the fact that the carrier is obligated to refund all expenses incurred as a result of the flight cancellations.
Ryanair promises that every customer involved will receive an email about the changes while the airline will promise either an alternative flight, or full fare refund.
The troubled Irish airline said it was it was slowing its growth this winter by flying 25 less aircraft from its fleet of 400 from November and 10 fewer of 445 from April.
They have also received a €40/£40 travel voucher, in additional compensation, for each cancelled leg of a flight though the terms and conditions prevent travel over Christmas.
Ryanair has cancelled another 18,000 flights, affecting 400,000 passengers this winter to "eliminate all risk of further flight cancellations".
Ryanair has taken a nosedive in reputation and share price due to the cancellations.
People walk to board a Ryanair flight at Stansted Airport, northeast of London, Britain, September 7, 2017. 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 Dec 2017. This flight voucher is in addition to the flight re-accommodation/refunds those customers received last week.
Ryanair said: "We have notified the Alitalia bankruptcy Commissioners that we will not be pursuing our interest in Alitalia or submitting any further offers for the airline".