I'm going to be in LA later this month, with an NZ 1 flight booked to AKL on 5 December (in PE). The boss now needs me to fly to London for a few days in early December, returning to LA in time to meet up with my existing NZ1 booking.

I have the option to fly LHR-LAX on 4 December, giving me a night in LA before LAX-AKL, but I'd really prefer in this instance to have an extra night in London then fly straight through with no stop. If I booked my LHR-LAX trip on NZ1 on the 5th, I'd have the two sectors of the same NZ1 trip booked on two different tickets. Is there any way that this can work? I'm guessing they'd never check me in at Heathrow when booked separately like this.