You might want to stock up at the grocery store for food before your next flight.

According to a new study by the travel comparison site, TravelSupermarket, passengers are being ripped off –in a very big way --when it comes to buying in-flight snacks.

Selling food aboard flights has become a real moneymaker for the airlines.

According to the study, markups on the prices of food items ranged from an average 241 percent for baked goods to a whopping 2,601 percent for hot drinks.

“Airlines realize they have a captive audience of potentially hungry mouths to feed once they close the aircraft’s doors,” said Bob Atkinson, travel expert at TravelSupermarket, which carried out the research.

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Here are some examples of items with large markups:

--A cup of tea on Ryanair: $4.00.  Made at home with tea bag: $.30

--Pringles on Wizzair: $3.20.  In store: $.41

--Budweiser on Thomas Cook: $ 6.14.  In-store: $1.33

--Check Mix on US Airways: $3.49. In store: $2.19

-- Kit Kat on Aer Lingus: $2.  In store: $.64

--A bottle of water on Jet2.com: $2.76. In store: $.06

(Note: All prices are based on items sold on Amazon.com or at Walmart.)

Bottom line, buying food at a local supermarket is often a good bet when it comes to the bottom line.  But even getting a last minute bite at the airport stores and kiosks will cost you less than on board.