Will I have to go through TSA again when I land at LAX? I'm coming in on United and leaving on New Zealand Air. I will be leaving Montana on United; it’s all booked on one itinerary through United and I go to New Zealand Air at LAX. I was just wondering once I get to LAX and I have to go into the international part of the airport, are you required to go through security to get into the international part or can I bypass TSA?
No, you will not go through the TSA again at LAX.
US airports make no distinction between departing domestic and international flights, since there is no passport control on departure. You will go through TSA security in Montana, board your flight, then arrive on the "airside" (post-security) of LAX and simply walk to your connecting international flight to New Zealand.
Note: This applies as long as there's airside connectivity between your arrival and departure terminals. This is the case for Terminals 7/8 (United) and TBIT at LAX, and more generally most through-ticketed connections on the same alliance at major airports, but this may not be true for all airlines at all airports.
Source: I had essentially the same transfer at LAX earlier this year (domestic-LAX-international on United).