ANC is the junior 747 base so let’s say you are going there. At the beginning and end of your trip Atlas will buy you a ticket from and back to your gateway. If you list HNL Atlas would book a ticket HNL-ANC. If you can find a ticket NZ~ANC that is cheaper they will book that for you. if not it’s up to you to get to HNL. You might be better off listing someplace like New Orleans as your gateway so the cost of a ticket is higher. But again if they find a cheaper ticket out of NEW you’re on your own. There’s no paying the difference and the IRS doesn’t consider your travel expenses as a deduction because they would think you live in ANC.