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Work on the $5.3 million project began earlier this month, and was expected to take six weeks to complete - weather permitting, he said.
A mobile asphalt plant had been set up at the southern end of the 1900m runway for use by the 65 Fulton Hogan contractors, who had come from all over New Zealand to work on the project.
''Because of the small window to do this - 9.30pm at night to 6am the following morning - the more asphalt we can put down in a single night the lower the cost is,'' Mr McCall said.
The 24-hour airport would be closed to flights after its last scheduled flight at 9.10pm and reopen at 6.30am, with work continuing between those times.
There would be some disruption to NZ Post and other flights, while medical flights would have to use different airports during this period.
''It has been something we have been unable to avoid.''
Each night, the old asphalt was milled to provide better adhesion and strength as preparation for the new layer of asphalt laid over the top.
''You have to start and stop a major project every night.''
The main runway upgrade includes shape correction as the runway ''moves over time'', with the rehabilitation work typically carried out every 10 to 15 years due to aircraft loads and environmental conditions, he said.
The airport company budgeted for the upgrade and, while it wanted the work to last 15-years, ''in reality it will most probably be between 10 and 12''.
Mr McCall said those using the airport would notice little apart from the temporary plant, but ''if they were really observant they might see some brand new asphalt laid on the runway''.