The flight Friday from Montreal to Val D'or, in Saganash's remote northern Quebec riding, was delayed by a half-hour as the MP was removed from the plane.
Saganash apologized Monday to Air Canada and fellow passengers for the "unfortunate incident" and admitted he has a drinking problem.
"Neither fatigue nor stress can justify what I did," the MP said in a written statement.
"I need help to overcome a medical problem, a dependence on alcohol, like far too many other Canadians."
NDP leader Tom Mulcair agreed to allow Saganash time to seek treatment. His office announced that the MP will "be temporarily withdrawing from his duties as an MP due to sick leave." He named several MPs to take over Saganash's shadow cabinet and riding duties.
While he insisted he's not trying to make excuses, Saganash, a longtime leader in the Cree community of northern Quebec, suggested his traumatic experience in a residential school as a child contributed to his alcoholism.
And he indicated the death of Jack Layton and his own short-lived bid to succeed the late NDP leader combined to worsen the problem.
"I know that profound scars were left on me because of my time in residential school. I never shied away from that," he said.
"The death of my friend and mentor, Jack Layton, also greatly affected me. Like him I needed a crutch. The leadership race wore me out, on top of taking me away from my children and loved ones even more often.
"Life on Parliament Hill can be hectic and exciting but it is also full of obstacles and pitfalls. Many of my colleagues can attest to this."
Saganash, who represents the riding of Abitibi-Baie James-Nunavik-Eeyou, briefly ran to succeed Layton but withdrew early from the race, citing family health issues and a lack of financial support.
Air Canada Jazz spokeswoman Manon Stuart would not provide details of the incident that resulted in Saganash's removal from the flight.
"What I can tell you is that we have a zero-tolerance policy with respect to passengers engaging in unruly behaviour," she said in an email.
"At Jazz, we strive to provide a safe and comfortable flight for our passengers and a safe working environment for our employees. Our crew dealt with the situation according to our standard operating procedure ... The safety of our passengers and crew is our top priority."
Saganash is not the first federal politician to run into alcohol-induced trouble on a flight.
In 2002, Liberal MP John McCallum, then defence minister, was not allowed to board an Air Canada flight from Ottawa to Toronto because he was deemed to have been drinking too heavily. He denied having a drinking problem but vowed to give up alcohol after the incident.
Last summer, Maygan Sensenberger, the young wife of Liberal Sen. Rod Zimmer, was charged with creating an alcohol-fuelled disturbance, including uttering threats against her husband, on a flight to Saskatoon.
Liberal MP Judy Sgro said the latest incident with Saganash is "just another time when elected officials, instead of gaining respect, I'm afraid are losing it."
"Maybe it's a symptom of the kind of frustration he feels around here because it's a very frustrating place to be," Sgro added. "Some people go to the gym. I guess other people decide to do different things."
Other MPs were reluctant to criticize Saganash's behaviour.
"I've learned in this business never to make comments about other colleagues," said Conservative MP Merv Tweed. "Everybody has their challenges."