I've just seen figures showing Qantas international passengers are spending millions of dollars a year on inflight shopping purchases.

The airline is recording nearly 350,000 duty free shopping transactions a year, with purchases ranging from sunglasses to tech gadgets.

That's just one airline and doesn't take into account purchases made through duty free outlets in airports; yikes, how much are people spending??

I'm not really into shopping – I think I was born without retail therapy receptors – but I know I'm in the minority.

Duty free shopping is a big part of the holiday experience for many travellers, along with the shopping they do at their destination.

Duty free prices do not necessarily represent big savings over discount stores and online sales these days, but there are still bargains to be had if you know what you're looking for.

I guess it is also hard to beat the convenience and novelty factor of having something delivered to you in your seat (although that takes away one of the few options for passing time in an airport).

You can even go online and pre-order what you want these days; Qantas says thousands of passengers per month take up this option, with pre-ordering available at least three days prior to departure.

The most popular item sold by Qantas is polarised wireframe sunglasses, followed by global power adaptors and vodka.

Making up the top ten are various other forms of alcohol, a travel photo lens set, lip balm and macadamia chocolates.

(Okay, so the macadamia chocolates and vodka I can understand.)

On the subject of alcohol, it seems that when we're not shopping during flights, we're very committed to drinking.

A company specialising in onboard sales technology for airlines, GuestLogix, analysed more than eight million transactions across five North American airlines and found passengers spend more money on alcohol than any other inflight purchase.

The figures relate to onboard consumption rather than duty-free shopping, on airlines where passengers purchase their own food and drinks.

Spirits accounted for just over a third of all sales, followed by wine at 13 per cent and beer at 10 per cent.

This equated to more than $40 million in alcohol sales in just four months – that's a lot of drinks, my friends.

Non-alcoholic drinks were just one per cent of sales, with fresh food items making up most of the remaining purchases.

Very few people shelled out for comfort items such as pillows and blankets, but headsets and inflight entertainment together accounted for four per cent of total sales.

GuestLogix found some passengers were spending more than $100 per flight on beverages alone, with flights to holiday destinations such as Las Vegas, Mexico and Hawaii not surprisingly recording the highest average sales.

The data also showed that Sundays were consistently the highest-revenue days for inflight sales across all categories.

There's a lot of talk about avoiding alcohol during flights – it can certainly affect you more at altitude and doesn't help with hydration levels, which are a big part of avoiding jet lag – but it does provide a distraction and help pass the time.

British Airways recently used hi-tech blankets to track passengers' emotions during various stages of flight and found eating and drinking made passengers a lot happier.

The fibre-optic blankets were linked to headsets that measured emotions with neuro-sensor technology, turning the blankets red when passengers were stressed or anxious and blue when they were calm and relaxed.

'Here's what we discovered: Initially, there are fluctuations as the passengers settle in, but there is a noticeable lift in a passenger's mood whilst enjoying food and drink," British Airways said.

While the blankets have proved a clever marketing tool for British Airways, they do serve a purpose: They are being used to help the airline analyse aspects of its onboard service, such as the timing of meals and entertainment options.

The colour-changing blankets can also help flight attendants identify passengers who are feeling anxious or stressed about the journey.

Maybe the standard response should be to take them a stiff drink and an inflight shopping catalogue.

Do you ever purchase duty free on board flights? What other items have your purchased on board? Post your comments below.

NOTE: This will be my last "Travel Insider" column. After nearly 20 years as a travel writer I have decided to pursue a new and very different career as a paramedic. Thank you to my loyal readers for all your feedback and comments over the years. Safe travels!

jane.fraser@fairfaxmedia.com.au