At Air New Zealand, operational problems were cascading early last year.
Problems with Rolls-Royce Trent engines were causing ripple effects that spread throughout the airline.
Initial problems with turbine blades spread deeper into the engines powering the airline's Dreamliners. When compressor blades were found to be faulty, Air NZ was forced to ground more of the planes for longer and some of those operating had restrictions on where they could fly.
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The wet lease of planes from Portugal's Hi Fly was expensive and not delivering what passengers wanted.
The airline needed to take control of the aircraft it was operating and that meant leasing something of a motley fleet of Boeing 777s.
But still the pressure on the network had reached a point where one in four Air NZ planes was running late. Its on-time performance (OTP) slipped to 76 per cent.
By the airline's definition, a plane is late if it arrives 15 minutes beyond the time on the ticket.
Carrie Hurihanganui flew back into the storm when she re-joined the airline, taking a place on its 10-member executive as chief ground operations officer in July last year after a short stint at the National Australia Bank.
She'd had 18 years with Air NZ before the job across The Ditch.
Hurihanganui began her airline career as a flight attendant in 1999 while she studied for her Bachelor of Business Management degree, and had numerous senior operational and corporate roles including international cabin crew manager, Auckland domestic airport manager, general manager of Eagle Air and general manager of offshore airports.
The Trent engine issues were grounding up to five of the airline's 14 Dreamliners at one stage as they needed to be assessed, and if necessary flown to Singapore for repairs.
Ripple effects were spreading throughout the airline's network of more than 3000 flights a week and although the problems mainly hit international flights, jet trunk operations and regional services were also affected.
With some understatement, she says: "There was definitely some frustration."
The airline aims to have 85 per cent of planes arriving on time. The big fall in punctuality saw it slide down global rankings — and a series of extreme weather events during the first half of 2018 didn't help either.
• If an Air NZ plane arrives more than 15 minutes beyond schedule it is late
• At one time its OTP slipped to 76 per cent, from the goal of 85 per cent
•During the last six months it has averaged 82 per cent
•Jetstar uses departure time to measure on-time performance
•During the past six months it has averaged 84.05 per cent across its regional and jet operations
The airline, with hundreds of others, uses Singapore-based aviation consultancy OAG to measure its performance.
Last year Air NZ slipped out of the top 10 for the Asia-Pacific region for the first time, with 76.70 per cent of flights on time during the year, five percentage points down on the previous year.
"On-time performance is the foundation of trust and confidence that our customers have — we say we're going to get you to your destination at the time you want to get there."
When OTP slips, too many of the airline's 17 million passengers a year are late for meetings, family events and other occasions.
Tactics to turn it around
"We really wanted to have a look," says Hurihanganui. "There has to be sustainable improvement within operating rhythm in our business structure rather than just a project — those have a limited impact."
The Trent engine issues were primarily affecting the international schedule — about a third of flying — so the aim was to ring-fence the rest of the operation.
"Across our regional and domestic network we wanted to make sure we were performing as strongly as possible."
The airline took a hard look at schedules and rebuilt them. In the same way that it works with safety by design, it adopted operation by design — long term processes baked in to the business.
"Block time (off the blocks, to on the blocks) was re-assessed. Some passengers over the past year have noticed scheduled flight times between Auckland and Wellington have an extra five minutes on them.
Hurihanganui says these sorts of changes were aimed at setting up ground crew for success.
"We don't want to set ourselves up to fail."
To reduce the ripple effect of delays, the number of crews swapping between aircraft has also been cut.
A new approach has been taken to turnarounds, where aircraft are disembarked, cleaned, reprovisioned with food and fuel, baggage unloaded then loaded, and then reboarded.
The airline needed someone to "quarterback" the whole operation and turnaround managers have been appointed.
Hurihanganui says those turnaround manager are in gates with visibility of the entire operation. The airline aims to turn around an Airbus A320 within 35 minutes.
Air New Zealand is also trialling artificial intelligence (AI) at one domestic gate at Auckland Airport to help make turnarounds more efficient.
Several cameras capture the whole operation, allowing time stamps at every stage. They not only provide more real-time information for turnaround managers, but also historical data.
"It's early days but as it's gathering data it will take us into the predictive analytics so you can expect on a day with this weather, this number of passengers and baggage — it will start to predict for us."
What's the outcome so far?
The re-entry of Dreamliners to the fleet after repairs has helped the airline recover OTP — only one is out of action and the imminent arrival of a new 787-9 will bring the operational fleet back up to 14.
It is keeping one leased Boeing 777 to provide backup if needed over summer. But the new measures implemented are also working.
Last month OTP was 86 per cent on the network and at one point in August Air NZ was sitting at 23rd out of 340 airlines, says Hurihanganui.
But over the past six months Air NZ's punctuality was sitting at 82.9 per cent.
Hurihanganui says the ability to recover is much better than it used to be and the airline is on track to make its schedule a little ''boring.''