Generally this is 20 Kg on International Flights and 16 Kg on domestic services. Some domestic flights might allow extra if you are a member of an "executive club" or have come from overseas as a Business Class passenger. For example see -- http://tinyurl.com/28ukh8 -- for Air Niugini baggage allowances.
Check with the airline you are travelling with for the amount of take on / carry on luggage you are allowed. As a rough guide allow about 5Kg in economy but CHECK with the airline.
Tags: baggage allowance