Another option is to fly to Auckland International Airport (AKL) in New Zealand, and then take a connecting flight to Fua'amotu International Airport (TBU) in Tonga. This flight takes about 5 hours and 30 minutes.
If you are traveling by boat, the journey from Fiji to Tonga can take anywhere from 24 to 48 hours. There are several shipping companies that offer regular services between the two countries, including the Fiji Shipping Company, the Tonga Shipping Company, and the Interisland Shipping Company.