Spain has fined five low-cost airlines €179 million for “abusive practices”, including charging for hand luggage.
Ryanair was fined the highest of €108 million (£90 million), followed by EasyJet's penalty of €29 million (£24 million).
Vueling, Norwegian and Volotea were sanctioned on Friday by the Spanish Ministry of Consumer Rights.
The ministry said it was considering banning practices such as paying extra for hand luggage and reserving seats for children.
These fines constitute the most significant sanction imposed by the ministry and follow an investigation into the low-cost air transport sector.
The ministry said it maintained the fines first announced in May after rejecting appeals filed by the companies.
Vueling, the budgetary arm of British Airways owner IAG, has been fined €39m (£32m), while Norwegian Airlines and Volotea have been fined €1.6m respectively million euros (£1.3 million) and €1.2 million (£1 million).
The fines were imposed because airlines provided misleading information and were not transparent about their prices, “which hinders consumers' ability to compare offers” and make informed decisions, the ministry said.
Ryanair has been accused of violating a range of consumer rights, including charging for larger carry-on bags, choosing a seat and charging “a disproportionate amount” to print boarding passes at terminals.
Each fine was calculated on the basis of the “illicit profit” obtained by each airline thanks to these practices.
Ryanair boss Michael O'Leary said the fines were “unlawful” and “baseless”, adding he would appeal the case and take it to European courts.
“Ryanair has used baggage fees and airport check-in fees to change passenger behavior for many years and we are passing these savings in the form of lower fares to consumers,” he said .
Easyjet and Norwegian said they would also appeal the decision.
ALA, Spain's aviation sector watchdog, plans to appeal and called the ministry's decision “absurd”, arguing that the fine violates European free market rules.
But Andrés Barragán, secretary general of consumer and gaming at the ministry, defended the fines, saying the government's decision was based on Spanish and European law.
“It's an abuse to charge 20 euros for just printing the boarding pass at the airport, (it's) something that no one wants,” he told the World Business Report program of the BBC.
“This is a problem that consumers face not only in Spain but also in other EU countries.”
Consumer rights group Facua, which has campaigned against the fees for six years, described the decision as “historic”.
