Flysolomons is the only airlines that allows extra baggage for international flights to the Solomon Islands for humanitarian reasons. The usual checked in allowance is 30kg. For domestic flights with Flysolomons the checked in baggage allowance is only 16kg, with a further cabin allowance of 7kg. (total baggage allowance 24kg).
Please contact firstname.lastname@example.org prior to your trip to Solomon Islands, so that a formal letter requesting extra baggage allowance for medical supplies can be issued to Flysolomons, who have a good track record of allowing an extra 10-20kg per person in checked in baggage.
We do not recommend the other budget airlines, as they have a bad track record when it comes to allowing extra luggage for humanitarian reasons. Qantas will only allow extra luggage for domestic travel within Australia.