Airlines around the world now charge passengers more if they want to enjoy the extra space offered in the emergency exit row on planes, but one carrier has run afoul of air safety regulators because of the practice.
London's Telegraph reports that European budget carrier Ryanair is under investigation by the Irish Aviation Authority for taking off with the emergency exit seats empty, after passengers refused to pay the £10 ($A15) charge to sit in the seats.
Passengers sitting in the exit row are required familiarise themselves with the evacuation procedures and to offer assistance in case of emergency and if they refuse to agree to this, can be moved to a different seat.
Ryanair has reportedly taken off many times with the exit rows empty and has instead instructed passengers other seats, further from the exits, on evacuation procedures. The practice has caused concern among the British Airline Pilots Association and Britain's Civil Aviation Authority.
A spokesperson for Ryanair said it did not believe the practice was a problem and that the airline complied with "all mandatory safety directives".
The investigation is the latest controversy for the airline, which has forged a reputation for trailblazing extra fees and charges for passengers, including a charge of up to $A105 to check a bag, as well as running afoul of advertising regulators over raunchy ads.
Qantas, Virgin Australia and Singapore Airlines are among the carriers operating in Australia that charge extra for the exit row.
Australia's Civil Aviation Safety Authority does not have specific regulations to determine who is allowed to sit in a exit row seat, but offers advice to airlines on the criteria they should use. This includes being able-bodied; a minimum of 15 years old; can understand and converse in English; are not travelling with an infant; are not travelling with someone who requires their assistance in an emergency and are willing to provide assistance to cabin crew and other passengers in the event of an emergency.
Follow the Traveller section on Twitter @FairfaxTravel