(Dallas, TX) — Southwest Airlines is confirming a human heart was accidentally left on one of its planes.

A spokesperson for the Dallas-based air carrier says the organ was discovered on Flight 3606 from Seattle to Dallas this past Sunday.  The plane ended up returning to Seattle, so the heart could be taken to a local hospital.  It isn’t known what medical facility received the heart.

Southwest Airlines says passengers had to wait five hours before being able to head to Dallas.  They’re promising to offer passengers a gesture of goodwill for what happened.