Revenues from travel retail, which also includes sales on planes, rose 9.4% in 2012 to $55.8 billion, according to a market study by Generation Research.
It should reach $60 billion this year and nearly double in size by 2020, the study forecast.
This channel is becoming very important, Bruno Pavlovsky, chairman of Chanel's fashion business, said. Customers are spending time in airports where the environment has become increasingly sophisticated.
The French luxury brand, the world's second-biggest behind Louis Vuitton by sales, has boutiques in four Asian airports and one at London's Heathrow, and next year will open a boutique in Paris Roissy Charles de Gaulle airport and another in Dubai.
Kering's Gucci, which like mega-brand rival Louis Vuitton has suffered a slowdown in the past two years partly due to emerging market shoppers' growing preference for logo-free products, has opened boutiques in the same locations recently.
Tourism spending is up 12% worldwide since January while spending by Chinese tourists in Europe is up closer to 20%, according to data from tax-refund company Global Blue.
Chinese tourists, who barely featured in luxury brands' customer statistics a little over a decade ago, now make up 29% of global luxury spending, consultancy Bain & Co said in a report published last week.
That trend is set to continue, with Boston Consulting Group forecasting nearly half of all air traffic in the medium term will come from the Asia Pacific versus 37% now.
Though most luxury brands raised prices, particularly in the euro zone and in Japan, to make up for currency moves, Bain estimates that over two thirds of luxury spending by mainland Chinese was made overseas in 2013, due partly to local duties.
According to Renaissance Capital, Europe remains the cheapest market for handbags with price 9% below those in Hong Kong and 28% below mainland China, while the yen's weakness has played in favour of luxury shoppers in Japan.
BCG expects the Chinese travel market will grow at a compound annual rate of about 11% from 2012 to 2030.
Chinese urban travellers took about 500 million domestic and outbound trips in 2012, spending about $260 billion, and it expects those numbers to increase to 1.7 billion trips and $1.8 trillion in spending by 2030.
Hermes, which has 50 boutiques in airports around the world, is turning these into proper free-standing shops to better tap the booming market.
This channel affects customers that are more interested in luxury than the average, said Patrick Albaladejo, deputy managing director of Hermes, adding that travel retail represented a significant portion of the brand's total sales.
L'Oreal, the world's biggest cosmetics group and maker of Lancome creams and Yves Saint Laurent lipstick, created a division last month dedicated to travel retail, which it described as a sixth continent.
Sales from travel retail generate 15% of total revenues at L'Oreal's luxury division and 12% for rival Guerlain, the perfume and cosmetics brand owned by LVMH.
Perfume and cosmetics represent the biggest product category for travel retail with 28% of the market, according to Generation Research, ahead of wines and spirits with an 18% market share, fashion and accessories with 13.5% and watches and jewellery with 12.2%.
LVMH, which owns Louis Vuitton, is planning to launch in 2016 a new retail concept called Galleria, specially designed for travel luxury shoppers, first in Venice and then perhaps in Paris, in the former Samaritaine retail building which is due to be converted into a five-star hotel.
Sales from LVMH's travel retail network, which includes duty-free shop chain DFS and Sephora cosmetics shops, another popular tourist destination, saw like-for-like growth of 19% in the nine months to September 30. The boost included contributions from LVMH's new DFS concessions in Hong Kong.
By comparison, sales from LVMH's fashion and leather goods, the bulk of which come from Louis Vuitton, rose by only 4% during the period.