“Oh my God, I think we… have a kid,” Wesley Branch told his girlfriend Ada Guan when their newborn baby first started crowning — 36,000 feet in the air on a flight to Tokyo.

Guan and Branch had no idea that they’d be welcoming their newborn daughter to the world while on a flight from Calgary to Tokyo on May 11, because Guan didn’t know she was 37 weeks pregnant in the first place. Yet, as the plane flew over Russia, Guan began experiencing acute pains in her abdomen, and thought she was just having a stomach ache. She was moved to the middle of the plane where she sat on the floor, and three doctors tried to determine what was wrong. Then her contractions started getting stronger, and she was moved to first class where she began giving birth.

“I got moved to first class because I could feel something wanting to come out,” Guan told CBC News. “So, that was probably the moment I knew. I thought I was just gaining a little bit of weight, and then this happened.”

Cryptic pregnancies, as they’re clinically named, occur in one out of every 450 women. They’re often unknown until the 20th week of pregnancy or later. The couple was completely surprised, as only a month ago Guan had taken a pregnancy test — the results came back negative. It’s possible this happened because the test couldn’t pick up human chorionic gonadotropin (hCG), a hormone that pregnancy tests look for, and one that also alerts the mother physiologically and psychologically that a baby is on the way.

Despite the sudden birth, the couple is ecstatic to welcome their daughter Chloe to the world. You can hear more about their surprise in the video below.