The Office of Fair Trading (OFT) has successfully taken action against 13 airlines which did not clearly display all fixed, non-optional costs, such as taxes, in prices on their websites.
As a result of the action, 11 of the airlines have already moved to make sure their sites display fixed, non-optional costs in their advertised prices.
However, Aer Lingus and Ryanair have changed their homepages but said that technical issues prevent them changing their whole booking process to reflect the prices.
The OFT said that it was satisfied that these airlines will make the necessary changes in the near future.
Sean Williams, OFT executive director, commented: "The OFT is committed to ensure that consumers are not misled by advertised prices that bear little relation to actual prices.
"Misleading pricing not only undermines consumer confidence but also distorts competition and we will enforce the law enthusiastically where we find that consumers have been misled."
The airlines which have so far changed their sites to make pricing clearer are easyJet, bmibaby, Flybe, Thomsonfly, flythomascook, Monarch, Jet2, Globespan, Wizz Air, Sky Europe and German Wings.
Earlier this month, the OFT fined British Airways a record amount after it admitted colluding with other airlines to artificially inflate fuel surcharges.
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