Another Canadian family has been prevented from boarding a flight this week because the father had signed his daughter鈥檚 passport for her. But he says it was a U.S. customs agent who told him he had to sign it.

On Wednesday, Nova Scotia dad Ahmad Hussein tried to board a flight to Washington from Halifax with his six-year-old daughter Mimi, but was stopped at the ticket counter. An Air Canada agent informed him that they weren鈥檛 allowed on the plane because Mimi鈥檚 passport had been rendered invalid.

Hussein has three children and all are frequent flyers. He says the only reason he signed his daughter's passport was because a United States customs officer told him to do so three years ago.

鈥淪o I did, thinking nothing of it,鈥� Hussein told CTV Atlantic.

The passport rules in the U.S. and Canada are different. In the U.S., a parent or legal guardian may sign a child鈥檚 passport if the child is too young to sign his or her own name.

But in Canada, the passport rules state: "parents/legal guardians must never sign a child鈥檚 travel document. Signing your child鈥檚 travel document will make it invalid."

Children under the age of 16 do not need to sign their passports, although those between the ages of 11 and 15 are encouraged to sign them themselves. A signature by a child under the age of 11 does not invalidate a passport.

Hussein says his daughter had used the signed passport several times since without a problem. But Air Canada says it has to follow federal government rules.

"This is not an airline decision and we are obligated to do so and will be fined if we do not," Air Canada spokesperson Isabelle Arthur told 麻豆传媒 in a statement.

A Montreal family ran into when they were prevented from booking a flight to Cuba after airline officials noticed they had signed their children鈥檚 passports.

Like that family, the only solution for the Hussein family was to order new, expedited passports from the Passport Office, and book new flights.

Air Canada was able to get Hussein and his daughter on a flight the next day. But Hussein says he wants to warn other parents to be careful about passport signatures.

鈥淚t's more of a warning not only for parents to look into this, but also for airlines to tell their clients this is something they should check if it's something that they are now enforcing,鈥� said Hussein.

With files from CTV Atlantic鈥檚 Kelland Sundahl