On a return flight to Baltimore, 62 stray animals left behind during Hurricane Maria were on board the aircraft.
"Each animal was boarded in the cabin of the aircraft in a crate which was secured into seats with seatbelt extenders," the airline said.
A veterinarian and volunteers from Lucky Dog were also on board to monitor the animals, WFAA TV station reported.
Puerto Rico is a Caribbean island and unincorporated US territory.
The humanitarian flight was organised after a call from Washington, D.C.-based Lucky Dog Animal Rescue regarding their Puerto Rican partner's need to relocate animals rescued before or after Hurricane Maria hit the island in late September.
"The devastation that Hurricane Maria caused the communities of Puerto Rico is heartbreaking," the report quoted Linda Rutherford, Southwest Airlines Chief Communications Officer, as saying.
Foster families in Puerto Rico had been taking care of the stray animals through the rescue organisation PR Animals.
It is not the first time Southwest Airlines has helped in the wake of a major hurricane. Two weeks before Maria hit Puerto Rico, Southwest rescued pets affected by Hurricane Harvey, which made landfall on the Gulf Coast in late August, the report said.
Hurricane Maria is considered the worst natural disaster on record in Puerto Rico. It is also the third-costliest tropical cyclone on record with a total of roughly USD 100 billion in damages.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)