He held an instructor rating in both hang-gliding and weight shift microlights but has been suspended and must resit exams before he can take to the air again.
Judge Keith de Ridder described the flight by Gross and a passenger as a "joyride".
Gross took off from Pohe Island in January 2016 and headed north and flew over Kamo.
He then headed south down the harbour, flew over the refinery inside the outer perimeter fence before flying at low altitude down Ruakaka Beach and inside the restricted area of the Marsden Point refinery before returning to Pohe Island.
During the return flight Gross flew directly over the top of the Whangarei Airport runway below the minimum height while the airport was operating.
"Throughout this particular flight you repeatedly failed to exercise the degree of care and attention that a reasonable and prudent pilot would have excercised," de Ridder said.
"In this particular flight, you demonstrated a very cavalier attitude towards both your responsibilities as a pilot in command and also towards the relevant rules and regulations."
He considered the offending to be moderate to high.
Gross told the Advocate after sentencing that the case had made local pilots more aware of the restricted area around the refinery.
He said while he broke the rules he believed he had not jeopardised anyone.
"It will make people more aware of how far out the restricted zone goes and hopefully make people more careful."
Greg McNeill, from Refining NZ, said the restricted airspace around the refinery was in place for safety reasons.
"Making fuel is inherently hazardous and requires a controlled work environment with good safety procedures. The danger to aircraft could be catastrophic should the refinery need to quickly depressurise units, with a sudden release of gas from the flare stack," McNeill said.
"Refinery workers are put at risk when an aircraft breaches the restricted airspace, the local community is potentially at risk, and, because the refinery is a critical piece of energy infrastructure, the wider economy too."
The restricted area was generally breached by pilots of recreational single-engine aircraft, helicopters, and microlights visiting the area over summer who were unaware of the zone.
No aircraft can fly lower than 3500ft within 1km radius of the tallest structure - a 120m-high, four-chimney flue - at Marsden Point Oil Refinery. If a pilot has to fly within the restricted area, they must apply for authorisation from Refining NZ.
"As the recent prosecution by the CAA underlines, they cannot just wander on through," McNeill said.
