Tests showed the pilot had 86mg of alcohol per 100 ml of blood. That's almost twice the New Zealand limit for drink driving of 50mg.
Drink driving, though, is perhaps a poor comparison to crewing a fully laden 350-tonne aircraft, which raises the question, is there a safe limit of blood alcohol to operate an aircraft?
To paraphrase the Dead Kennedys: when is a pilot "too drunk to fly"?
In Monaghan's case he was found to be four times over the limit set out in the UK's Transport Safety Act, which says that crew members shouldn't start flight duty with a blood alcohol level over 20mg of alcohol per 100ml of blood. Any crew member caught over this limit can be charged with "exceeding the prescribed alcohol limit" and being "unfit for duty".
However, the Civil Aviation Authority's official line is that "there is no measurable level of blood alcohol that is safe for aviation".
A pilot with a very low alcohol level might not be breaking the law, but it's the CAA's decision as to whether they can keep their license.
CAA New Zealand insists on a zero blood alcohol level but it's still possible to be deemed "unsafe" because of previous drinking. Nursing a hangover could be grounds for action against a flight engineer, though it would have to be obvious to crew members.
Most airlines operate "Bottle to Throttle" policies that dictate how long crew must leave between their last drink and active flight duty. Air New Zealand has a 12-hour no drink rule.
As abstemious as aircraft crews might be, this can cause complications for coordinating flights.
In 2014, Air New Zealand flights were stranded in Hawaii after crew members had been drinking. Members of two standby crews had been soaking up the atmosphere in Honolulu leaving flight coordinators with a massive headache.
After the departure of a Boeing 767 was aborted because of technical issues, 227 passengers were stranded for 56 hours as there were not enough reserve crew members sober enough to staff their planes.
A standard staffing of a 767 is three pilots and seven cabin crew, or just enough for Hawaiian-themed cocktail party.
It seems an airline pilot can never let their guard down.
Naturally a drink-driving offence is a stain on any professional's record, but it is particularly serious if your job involves the charge of a large aircraft and the hundreds of lives onboard.
"The CAA considers a drink driving episode to be a warning or a 'red-flag' incident, whether or not a conviction ensues."
It is not easy for a pilot to return to their flying career after developing patterns of problem dinking but it is not impossible.
As many as 50 Kiwi pilots and aviation professionals have been rehabilitated thanks to a scheme called the HIMS programme.
Developed in the United States during the 1970s, HIMS has helped about 4500 pilots over their problems and get back to work.
Speaking at a conference organised by Aviation New Zealand, Air New Zealand pilot and reformed alcoholic Captain Simon Nicholson praised the initiative.
"We are saying to the company 'please help this person, don't sack him, pay him please if you can while he is going through rehab, and hold his job for him'," he said.
Drinking on duty has traditionally been a sackable offence for pilots but Captain Nicholson said this tough stance is inclined to make flying not safer but more dangerous.
Pilots are less likely to come forward with their struggle with drink and colleagues more likely to cover for them.
Captain Nicholson helped get the New Zealand branch of the programme off the ground and win support from the CAA and Airways Corporation.
"There are pilots and air traffic controllers who have succeeded in demonstrating adequate treatment and ongoing safe behaviour, after severe alcohol problems," said the New Zealand CAA "and [they] have returned to being safe and active operational members of our aviation community."
