Air Canada planes get de-iced on the tarmac by crews at Pearson International Airport in Toronto, January 20, 2014.

An Air Canada passenger traveling to Toronto from a weekend in Quebec City found herself stranded alone on the tarmac and in the dark, in what she described as a "nightmare."

Tiffani O'Brien fell asleep aboard her June 9 flight only to wake up hours later in an empty, dark and locked plane. In a post shared by a friend of hers to Air Canada's Facebook page on June 19, the St. Thomas, Ontario, resident said she was "freezing cold" and surrounded by "complete darkness."

"I thought, this is a nightmare," O'Brien told CTV News in an interview that ran over the weekend. "This is not happening. I'm having a bad dream. Wake up, Tiffani."

Robin Smith, a spokesman for the Toronto Pearson Airport, said the airline confirmed the incident, adding that airport officials were "aware of this passenger's story and we can certainly empathize with the concern she must have felt." He referred further comment to Air Canada.

Air Canada spokesman Peter Fitzpatrick said the airline was "still reviewing this matter, so we have no additional details to share, but we have followed up with the customer and remain in contact with her."

The airline told the Associated Press it was looking into how the sleeping passenger was left on the plane.

"I just woke up alone in plane," O'Brien texted her friend Deanna Noel-Dale around 11:45 p.m. local time that night, according to text messages published by CTV News.

She tried to Facetime with Noel-Dale, but her phone's battery died, and the USB outlets were useless without the plane's power turned on, according to CTV News.

She then made her way to the cockpit, finding a flashlight and using it to make "SOS signals" out of the plane's windows, O'Brien told CTV News. When that got no response, she managed to unlock the plane's door, only to find the drop to the tarmac was too far for her to jump and the plane was parked far away from the airport terminal, she told the Canadian news channel. She then resorted to shining the light out the plane's door for help.

Meanwhile, Noel-Dale called Toronto Pearson International airport to alert them that her friend was still inside the plane, The Washington Post reported.

"When I see the luggage cart driving towards me I am literally dangling my legs out of the plane ... he is in shock asking how the heck they left me on the plane," O'Brien said, according to the Facebook post Noel-Dale shared to Air Canada's page.

O'Brien told CTV the incident has affected her work and that she now struggles to sleep, "waking up anxious and afraid" that she is alone and trapped "some place dark."

"It's just a sheer sense of helplessness when you feel like you're locked on this aircraft," O'Brien told CTV News, "and you have no connection to the outside world."

Noel-Dale didn't return a message for comment, and an attempt to reach O'Brien was unsuccessful. Noel-Dale told The Washington Post that she and O'Brien were declining to comment beyond their previous statements on the advice of a lawyer.