The airline fired Anna MacArthur in December 2008.
In October last year the Employment Relations Authority (ERA) ruled the dismissal was justified.
Ms MacArthur, who had worked for Air NZ since 1983, entered a recovery agreement with the company after she revealed in 2007 she was addicted to party pills.
At her own expense she flew to the United States for treatment and the agreement meant she could carry out ground duties as long as she stayed clean, attended counselling and was reviewed by medical staff.
After three months she would be assessed to see if she was able to return to flight duties.
However, 19 months later, the airline, while noting Ms MacArthur had made progress, dismissed her as there was still no definite date she could return to flying.
Last night Ms MacArthur told 3News the airline discriminated against her after it came out in support of pilot Warwick West, who had concealed three drink-driving convictions from his employer for almost 20 years.
"The pilots are obviously a lot more valuable to the airline and the cabin crew are expendable," she said.
"So I would imagine my recovery would have been more successful had I been a pilot."
But the airline said Ms MacArthur received "extensive rehabilitation assistance" when she asked for it, but afterward was still unfit to carry out her work.
"Safety of our customers is paramount in the airline's assessment of whether someone is able to return to their normal duties and in Anna's case, after almost two years, she was still unfit to fly and was dismissed on the grounds that it was unclear if, or when, she would ever be fit to return to work as a flight attendant," the airline told the New Zealand Herald.
Ms MacArthur said the contrast between the airline's treatment of her and Mr West would be detrimental for it.
"I would suspect that cabin crew would go deep underground and it wouldn't be until they were caught with random drug or alcohol testing, before they were discovered," she said.
In her ERA hearing, Ms MacArthur argued the recovery agreement had no definite end point and Air NZ could have made more of an effort to find her alternative employment.
She also said it was inappropriate for Air NZ medical staff to release her medical information to management, which breached her employment conditions.
However, ERA member James Wilson said that while there was no doubt Ms MacArthur was committed to rehabilitation and wanted to return to work, it was difficult to fault the airline's actions and on balance it was justified in dismissing her.
He did not accept the argument it was inappropriate for her medical information to be released to the company.
