The 23-year-old's labour was aided by a doctor on the AC009 flight, the Japan Times reported.
The plane was given landing priority and touched down 30 minutes ahead of schedule, said reports.
"I couldn't imagine, this just happened completely unexpectedly. It turned out we have a little baby, beautiful girl," said the unidentified father to Japanese reporters as he held the baby.
"Her name is Chloe."
The mother and newborn were taken to hospital.
On its website, Air Canada says women having a normal pregnancy and no history of early labour can fly up to and including their 36th week. A typical pregnancy lasts 38 weeks.
The airline tweeted that mom and child are doing well.
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