Suponho que você esteja pilotando o voo Londres-LAX-Auckland da Air New Zealand. Então o site deles diz que você precisa de um visto ou ESTA:
Changes to LAX transit process for customers travelling between Auckland and London Heathrow on NZ1 and NZ2
On arrival at LAX, transit customers continuing on the same aircraft to Auckland (NZ 1) or London Heathrow (NZ 2) will be directed by ground staff down to US Customs and Border Protection processing. Following, passengers will then be directed to a designated transit location for security screening by the Transportation Security Administration (TSA). Once screened, passengers will be directed back into the central terminal area where they will have complete access to the departure area, including the 150,000 square feet of retail and dining space in TBIT’s Great Hall. For those eligible (Business Premier, Star Alliance Gold & other eligible customers), transiting passengers will also have access to the Star Alliance Lounge. Passengers must retain their boarding passes at all times. There is no requirement to complete any arrival forms and checked baggage will remain onboard during transit time. Customers are still required to meet all entry requirements including having a current visa or ESTA where applicable.