A clampdown on hidden fees imposed on passengers by airlines is set to be launched by the Civil Aviation Authority (CAA).
Reviews into every airline selling tickets in the UK will assess whether costs are presented in an "open and clear" way to prevent travellers being saddled with unexpected extra expenses.
Charges for basic services such as name changes, checking in at the airport rather than online and re-issuing boarding passes will be scrutinised by the watchdog.
Currently, changing the name on a flight ticket costs £160 with Ryanair, up to £50 with easyJet and £35 for short-haul flights or £50 for long-haul flights with Thomas Cook.
Choosing to check in for a Ryanair flight at the airport instead of through its website can land passengers with a bill of £45.
And to get a boarding pass re-issued at the terminal by the Irish airline requires a payment of £15.
A CAA spokesman said the investigation is "about making sure airlines are open and clear so that people understand what they are actually paying for".
He added: "You've got the headline price of the ticket, but are there any additional things that people have to be aware of that they will have to pay for?"
Aviation minister Robert Goodwill recently faced calls to challenge Ryanair over the costs associated with amending travel documents with the airline.
He said this week: "The Government and the CAA continue to emphasise to the airlines the importance of compliance with ticket transparency obligations, ensuring that terms and conditions - including any administration fees and charges - are clear to passengers when they choose between airlines.
"To enhance consumer protection in this area, the CAA will start work on unfair contract terms with the airlines this summer, in accordance with the CAA's Strategic Plan 2016-2021.
"The work will include a review of the airlines' terms and conditions with the aim of ensuring the rights and obligations of the consumers and businesses are fair and balanced and consumers are not being penalised by unfair contract terms."
Two cases are currently being prepared against airlines by legal website CaseHub - including one concerning Ryanair and the matter of fees.
CaseHub founder Michael Green said the case involving Ryanair will claim charges to check in at the airport, re-issue boarding passes and name-fee changes are unlawful.