Amadeus saw a 85% jump in ancillary revenue through online travel agencies during the first three quarters of 2015.
It says OTAs are now a major channel in the merchandising market with up to 40% of all OTA bookings including ancillary products for some airlines.
The exponential growth of ancillary fees through OTA channels is a result of customer demand and the availability of ancillary content in the GDS, said Pedro Espin, associate director for merchandising and personalisation at Amadeus.
"Online travel agencies constantly need to improve their user experience to stay competitive. If I want to book a window seat or bring one extra bag, and an OTA does not give me that option, I can find another travel vendor in just a few clicks," Espin said.
Amadeus said there are currently 60 airlines selling ancillaries and Fare Families (groups of fares with the same characteristics) through the system, with an additional 40 signed and going through the integration process.
"The selling of merchandising is the first step that OTAs are taking in offering travellers great personalisation in their air bookings. This trend will benefit everyone – travellers, OTAs and airlines," Espin added.
Amadeus said that by the end of the year, the number of OTAs with integrated ancillaries is set to almost triple compared to a year ago.
OTAs selling ancillaries or fare families include Expedia, eDreams, Logitravel and Tripsta.
