Upvote:5
It depends, if the airline provides one of those "IF IT FITS" boxes to check the size of the carry on, then it might be refused. For example, EasyJet:
Anyway, 2 cm will not be easily noticed by bare eyes, so if the airline does not have the baggage checker at the gate I would take the chance as long as the weight is within the limit. Remember, if the airline has the baggage checker, it is better to pay for the extra size online, it will be much cheaper than paying at the gate.