When Kathleen Considine had last seen her dog Jacob at her parents' home in Dearborn, Michigan, he was the loveable, playful ball of energy one would expect to find in a 7-year-old golden retriever.

But when the pair was finally reunited in Considine's new hometown of Bend, Oregon, after two months apart on January 29, she wasn't greeted with the sweet tail-wagging and sloppy kisses she so fondly remembered.

"The second that Jacob looked at me in the eyes, I knew that something was wrong,” Considine told Travel + Leisure, reflecting on what unfolded after his two-plane trip to meet her. Jacob had just completed the journey from Detroit to Portland with United Airlines, including a one-hour layover that turned into 20 hours after his carrier didn't fit on the second plane.

Considine says staff at Detroit Metropolitan Airport mistakenly assured her mom, who dropped Jacob off, that his carrier would fit on both planes, but that she then received a call from staff at Chicago's O'Hare saying he was being put in a kennel until a plane with enough space could take him to his final destination. He didn't depart until the following afternoon.

Image zoom Courtesy of Kathleen Considine

When Considine's boyfriend, Shane, arrived at Portland International Airport to bring him home, he could tell the dog wasn't being himself.

“It took him a while to even get up and get out of the cage, which is very unlike him,” Considine said. “I thought, he's had a long couple of days, he's probably exhausted.” But as the evening went on, Jacob's condition took a turn for the worse.

Considine was trying to make him comfortable, at the advice of the local emergency vet, when he became unresponsive: “Jacob looked at me, stood up, went to the end of the bed, stretched out really crazy and then closed his eyes. I couldn't tell if he was breathing or not at this point.”

That's when she and Shane carried the dog to the car and rushed him to emergency care. Jacob's heart was still beating and the vet performed CPR immediately, but after eight minutes, they lost him.

Image zoom Courtesy of Kathleen Considine

Jacob had passed a physical the day before his flight, but the vet told Considine the cause of death was Gastric Dilatation and Volvulus Syndrome, a bloating condition that causes the stomach to dilate and twist into an abnormal position. It can be caused by over-eating or stress. “It's a really terrible disease that can happen anytime, especially to larger, big-chested dogs... there's no saying if he stayed at home he wouldn't have gotten sick,” Considine said. “But it's the way [the airline] handled the situation and the fact he was on the plane for so much longer than he was supposed to be—that's where I find the problem.”

Considine spoke out about the ordeal via Facebook on Friday in a post that now has thousands of shares and comments, with total strangers offering everything from sincere condolences to furious plans of action.

United Airlines' PetSafe program is an “industry leader” in animal travel, Charlie Hobart, a spokesperson for the airline, told Travel + Leisure, calling any incidents “extremely rare.”

“We handle about 200,000 pets per year, and we have a team of trained professionals dedicated to their safety and comfort,” he said, adding that Jacob “showed no signs of distress” while in the airline's care.

Animal incidents on airlines are rare: From January 2016 to October 2016 (the last month for which data is available), there were 23 deaths, 20 injuries and zero losses, according to the Department of Transportation. However, the Humane Society suggests looking into every available alternative before transporting a pet on an airplane.

Considine says United showed her no sympathy until a head from the PetSafe department (who said she had been traveling internationally) called and apologized two weeks later, issuing her a refund. “I feel like they only reached out to me because of what I did on Facebook, because they were nothing but rude before that,” she said. United Airlines said it would donate $500 to the charity of Considine's choice in memory of Jacob.

Image zoom Courtesy of Kathleen Considine

Above all, Considine said her goal in sharing her devastating story is to make sure no one else has to experience the pain she is going through. “I've received a lot of messages from people saying they'll never fly their dogs again,” she said. “I know when I decided to put him on a plane if I heard of anything like this, I wouldn't have done it. There's no way. So hopefully me getting the word out will help other pet owners in the future.”

On February 20, Considine launched a GoFundMe page to raise funds to "offset lawyer fees in hopes of starting a non-profit foundation to make airline travel safe for pets."

"My goal now is to become an avid supporter in the efforts to improve aviation safety and protocol for our pets," she wrote. "I'd like to start a non-profit foundation to help make these changes and ensure longevity in the safety and health of our pets who need to travel. Setting up an organization such as this requires a lot of legal work, so I am reaching out to my supporters so together we can make this happen."