United Airlines flew the wrong dog to Japan just days after a bulldog puppy died when it was locked inside an overhead locker.

Owner Kara Swindle shipped her beloved German shepherd Irgo to Kansas, where the family are moving to from Oregon. But when she arrived at a United cargo facility in Kansas City on Tuesday, the 10-year-old pooch was missing.

In his place, she found a Great Dane that was supposed to be en route to Japan, CNN reported.

Both dogs had been in Denver, where they were set to catch connecting flights.

Swindle, who adopted Irgo when he was four, told CNN that they (the airline) had no idea where the dog was.

"I burst into tears instantly because this has just all been a whirlwind. They didn't know (where Irgo was) until 2.30am on Wednesday when the plane landed in Japan.”

The owner said first-time flier Irgo had no food or water on the 16-hour flight to Japan and had not been given medication for an ear infection for three days.

Vets in Japan examined the dog and deemed him fit to fly.

Irgo has been flown from Narita, Japan, Kansas in a private charter, Swindle said.

United Airlines has apologised for the mix-up and said an investigation is underway.