A marketing expert says Jetstar's deciding to charge for overhead carry-on luggage is is just business. 

From February, all passengers' under-seat luggage can weigh more - up to 10kg - but they'll have to fork out an extra $23 for overhead luggage.

Auckland University marketing professor Mike Lee says it's an attempt to separate itself from other carriers. 

"This will rationalise some of that premium overhead space now - and then, of course, they'll be making a nice little profit on that, hopefully." 

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