Italy's antitrust authority on Thursday slapped fines on low cost airlines Ryanair and Wizzair over their cabin baggage policy.
Both carriers allow small bags into the cabin free of charge only if they can be stowed under the seat in front of passengers.
Bigger bags of up to 10 kilos require a luggage fee, or a fee-paying priority boarding pass.
Ryanair was fined three million euros ($3.4 million) and Wizzair one million euros.
The Italian antitrust agency said that most passengers expected to travel with a larger carry-on bag and that by imposing an extra payment of between 5 and 25 euros the airlines were raising ticket prices in a "non-transparent" manner.
After Ryanair announced its new cabin bag policy in August, Italian regulators ordered the airline - as well as Hungary's Wizzair - to suspend the measure, saying it misled consumers and distorted competition with carriers that transported cabin luggage for free.
Ryanair rejected the Italian decision, saying its policy was transparent and helped flight punctuality as it speeded up boarding.
It went into effect in November.
Explore further: Italy tells Ryanair, Wizz Air to suspend bag charge