Airlines face review over extra charges for passengers
The Civil Aviation Authority is to investigate extra fees charged by airlines on top of basic ticket prices.
The review will decide whether airlines are "open and clear" with passengers about what they are paying for.
After the "headline price" of a ticket, customers may have to pay to change a name on their booking, re-issue boarding passes or check in at the airport rather than online.
Ministers say the CAA will examine whether any charges are "unfair".
Additional charges can add a significant amount to the basic ticket price and have long been the subject of complaints by passengers.
Changing the name on a ticket costs £160 at the airport or by phone with Ryanair, up to £120 with Monarch, up to £70 with Thomas Cook and up to £50 with Easyjet.
Checking in for a flight at the airport rather than online costs £45 with Ryanair, and is free with Easyjet.
Re-issuing a boarding pass at the airport costs £15 at Ryanair and £17.50 at Jet2.
The CAA says "anything that is an additional charge will be looked at", suggesting it will also look into the transparency of charging for in-flight meals, advance seat selection, paying by credit card and putting bags into the hold.
BBC correspondent Jane-Frances Kelly says that while airlines are within their rights to make these charges, the CAA wants to make sure they are fully transparent and not hidden away until it is too late for customers to go elsewhere.
The watchdog has the ultimate sanction of taking court action, under the recently introduced Consumer Rights Act, which is aimed at protecting customers from charges and conditions hidden in small print.
It also publishes a list of individual airline charges on its website.
Aviation minister Robert Goodwill 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.
"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."
The CAA says its review will take "a few months" at the end of which it will publish its findings.
Legal website CaseHub has been preparing a class action legal case against Ryanair, arguing that the airline's fees to check in at the airport, re-issue boarding passes and change names are unfair and against EU consumer law.
Ryanair says its optional fees are transparent and allow it to hold down ticket prices, while other terms and conditions are set out clearly on its website.
Correction 20 June 2016: This article was amended to reflect the fact that Easyjet offer free airport check-in, contrary to information on the CAA website.