"There is still no information here about how expenses will be treated where passengers are re-routed to and/or from other airports or where they otherwise incur additional out-of-pocket expenses as a result of the cancellations", the CAA said.
The Taoiseach has said he expects Ryanair to ensure that passengers' rights are protected.
Every customer affected by the cancellations is also entitled to a travel voucher for a €40 one way flight or €80 for a return flight valid for travel in October or March.
Passengers affected by the new measure, "less than 1% of the 50 million customers we will transport this winter" received an email to inform about these changes and "offer alternative flights or total refunds".
The airline initially blamed a rota mistake, leading to a shortage of available pilots.
Wilson said that while customers were bearing the brunt of this cancelled flights fiasco, investors are just as anxious about rising labour costs affecting Ryanair's low cost model.
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The CAA did not say what action it would take if Ryanair did not comply, but it has the power to take court action against carriers that fail to comply with consumer rights laws.
"If they follow through on what they are saying, then they would be breaking the law".
The Civil Aviation Authority said the Dublin-based company failed to provide details of compensation and falsely claimed it did not have to re-route passengers on to other airlines.
However, it has emerged that Ryanair may force customers seeking flights with another airline in lieu of a cancelled Ryanair flight may be told to take busses or drive themselves in hire cars instead.
The warning said the company had until 5 p.m. Friday local time to put in place an "orderly explanation" about re-routing and reimbursement of expenses after a string of cancelled flights.
As it did when announced the first round of cancellations, the CEO of Europe's leading low-priced airline, once again called for "heartless apologies" to affected customers.