Budget airline Ryanair has been fined £24,000 for misleading customers about the price of flights.
The allegations related to the cost of flights from London Stansted
A jury at Chelmsford Crown Court found that the Dublin-based firm was guilty of six breaches of the Consumer Protection Act.
Trading Standards officers, who brought the prosecution, argued that Ryanair had failed to spell out the full cost of seats.
Ryanair had denied any offence and said the prices were not misleading.
The allegations related to the cost of flights from London Stansted to various European destinations.
Trading Standards claim the cost of insurance and tax was not included in the initially advertised price on the company's Internet website.
Ryanair, which has an office at Stansted Airport in Essex, claimed customers were told the fare did not include tax charges.
Last month, a judge ruled that 10 allegations that the airline exaggerated the cost of the flights on its website two years ago should be dismissed.
Essex County Council brought the prosecution against Ryanair because it said it had a moral obligation to stand up for consumers.
Trading Standards cabinet member Peter Martin said: "Essex County Council has fought to ensure that British consumers have the same protection under the law as their European counterparts.
"The price you see should be the price you pay - pure and simple.
"The case we encountered here with Ryanair was akin to going to a petrol station advertising fuel at 29p and then being billed an extra 60p in tax at the till not to mention an extra sum for short term parking."
Ryanair's head of customer services Caroline Green said: "The case confirms that Ryanair's internet banner headline advertising, which clearly excludes taxes, fees and charges, was not misleading to consumers."