Budget carriers such as easyJet and Ryanair will be scrutinised by the Civil Aviation Authority over hidden fees.
The probe is due to hidden costs that can range from a £35 to £160.
Basic services such as checking in, changing a name on the ticket and reissuing boarding passes are to be brought under the microscope.
Ryanair charges the highest amount to change a name on a ticket. The budget carrier charges up to£45 to check in and a further £15 to re-issue a boarding pass.
The CAA will take a look at the practices of each UK airline to ensure that all cost and charges are displayed in an ‘open and clear’ way.
The purpose of the probe is to ensure that passengers are getting what they have paid for and to make sure they are not being caught out by a headline price that has hidden charges.
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".
The decision by the CAA to open the investigation brought a forthright response from Ryanair.
A spokesperson for the budget airline said in a statement: "All Ryanair charges and fees are clearly outlined on the Ryanair.com website and throughout the entire booking process.”
They added, "Customers are asked to ensure that the details they enter at the time of booking are correct before completing their booking and we offer a 24 hour ‘grace period’ to correct minor booking errors."
Written by: Team Flight-Delayed