The European Commission said on Monday that low-cost carrier Ryanair (RYAAY) must comply with EU regulations on passenger rights regarding its cancellations of flights during a six-week period, the Financial Times reports.

The Commission added that Ryanair might have to reimburse and compensate passengers for the cancellations of between 40 and 50 flights per day until the end of October.

Ryanair has warned that the penalties could amount to 20 million euros (about $23.9 million) in compensation.

"Airlines operating in the EU need to respect the European rules.... Passengers whose flights are cancelled have a comprehensive set of rights," a Commission spokesman said.

"We have to check if all this is respected by Ryanair. For instance, you are entitled to reimbursement if you are not warned two weeks in advance," he added.

Shares of Ryanair were falling in late morning trading on Monday.

More of What's Trending on TheStreet:

More from Stocks

'I Think the Tech Sector is Changing the World,' Says Coupa CEO

'I Think the Tech Sector is Changing the World,' Says Coupa CEO

Natural Gas Could Be a Warm Place for Investors Fleeing a Frigid Market

Natural Gas Could Be a Warm Place for Investors Fleeing a Frigid Market

Uber vs. Lyft: The Tale of Two Ride-Hailing Companies Going Public in 2019

Uber vs. Lyft: The Tale of Two Ride-Hailing Companies Going Public in 2019

2 Well-Known Stocks You Should Consider Shorting This Week

2 Well-Known Stocks You Should Consider Shorting This Week

Why Jim Cramer Is Holding Off on Buying Nvidia Stock

Why Jim Cramer Is Holding Off on Buying Nvidia Stock