Dog Dies on Delta Air Lines

Another dog took off on a commercial airliner and when the plane landed ... it was dead.

Alejandro the Pomeranian was in the cargo hold of a Delta Air Lines jet that originated in Phoenix and was supposed to land in New Jersey with a stopover in Detroit. When the plane landed in the Motor City, we're told the 8-year-old Pom was alive ... but it was discovered he'd died during the process of transferring him to the connecting flight.

So far the cause of death has not been determined. Delta tells TMZ it's conducting a thorough investigation to find out what occurred to ensure it doesn't happen again. The airline says it's working with Alejandro's family to support them and has offered a free necropsy to have Alejandro evaluated.

The dog was owned by a unmarried couple that was relocating to New York.

The lawyer for the family, Evan Oshan, tells us ... from what he knows Delta has been pushing people to put their dogs in the cargo hold rather than the cabin, presumably because there are so many service dogs on board these days the passenger areas resemble a kennel.

Delta, however, tells us it did not push the passengers to store their dog in cargo ... it was their choice.