The airline said the passengers “clearly did not receive the standard of care to which they were entitled”.
The incident during boarding for a flight on August 26 from Las Vegas to Montreal was described in detail by another passenger, Susan Benson of New Brunswick, who said she was in the row behind two women and a man.
“There was a bit of a foul smell but we didn’t know at first what the problem was,” she wrote on Facebook three days later. “Air Canada attempted a quick cleanup before boarding but clearly wasn’t able to do a thorough clean.”
She said workers sprayed the area with perfume to hide the smell.
The passengers assigned to those seats were said to have told a flight attendant that the seat and seatbelt were wet and they could still see vomit. The attendant and a supervisor are understood to have told them that the flight was full, and they would just have to sit there.
The women were attempting to use blankets and wipes to settle in when one of the pilots showed up, Ms Benson wrote.
She said the pilot told the women, who were on their way to Vienna, that they could leave and book new flights at their own expense “or they would be escorted off the plane by security and placed on a no fly list!”
She said the pilot accused the women of being rude to the flight attendant, which she disputed - “they were upset and firm, but not rude!”
Security then escorted the women off the plane.
Asked if it would dispute any of Ms Benson’s account, Air Canada did not respond.
In its statement, Air Canada said it was still reviewing the matter on Tuesday and has contacted the passengers “as our operating procedures were not followed correctly in this instance”, adding: “This includes apologising to these customers, as they clearly did not receive the standard of care to which they were entitled, and addressing their concerns.”