The world is aghast after learning many of the 500 French bulldog puppies on a Ukraine Airlines Flight arrived dead at Toronto's Pearson International Airport on June 13.

A spokesperson stated that 38 of the puppies were dead on arrival, and that the Canadian Food Inspection Agency is investigating the circumstances of the tragic incident.

Dozens of the puppies aboard the flight from Kyiv arrived seriously ill and dehydrated. Video shows what appear to be people loading many crates of puppies at the airport in Kyiv.

So how did this happen?

According to Émilie-Lune Sauvé, senior campaign manager for Humane Society International, it's an ongoing problem with puppy mills which HSI/Canada has been working for more than a decade to shut down.

"It is devastating that the problem we are trying to address domestically is being compounded with the import of an unknown number of dogs from commercial breeding facilities that are as bad or worse in other parts of the world. These dogs are imported to be sold into the pet trade, often to unwitting consumers."

The problem, however, goes beyond puppy mills. Airlines need to do a much better job of screening their cargo to ensure they're not part of the problem.

In this case, it appears Ukraine International Airlines did now follow proper codes to transport live animals safely.

Most Canadian carriers only allow two animal crates per flight and don't fly with caged animals if temperatures are above 29.5 C.

"Plane transportation can be safe for dogs when the proper precautionary measures are taken. Unfortunately, for puppy mills and the brokers who source from them, animal welfare always comes second to profits," says Sauvé.

"Overcrowding, inadequate caging, transporting in extreme temperatures, lack of care in transit and shipping sick animals can all contribute to mortality in transit."

Sauvé says the best way to prevent situations like this from occurring is to adopt from rescue groups or shelters. If you must purchase from a breeder, make sure to see the facility firsthand and do your research before buying.

"There are many reasons this tragedy occurred," says Sauvé. "While many larger airlines have strict standards pertaining to animal transport, others need to improve their policies to ensure this kind of tragedy can't happen."