Prince: Singer with Him During Plane Overdose ... Also with Michael Jackson Days Before He Died

Even in death, Prince and Michael Jackson have something in common -- singer Judith Hill, who is opening up about what she saw the night Prince overdosed on his private jet.

Hill was on board the flight that made the emergency landing in Moline, IL ... and says she was talking to him when "his eyes fixed" and he nodded off. She told the NY Times she would have thought he just nodded off if she hadn't been "looking into his face."

But she says she immediately realized it was a medical issue and alerted an assistant and the pilot to put the plane down. TMZ broke the story -- Prince had suffered an overdose on Percocet, and emergency responders had to give him a save shot.

Hill -- who spent long hours recording and performing with Prince at Paisley Park -- NEVER mentions anything about his addiction. She refused to discuss his treatment in Moline, but said he reached out to Dr. Michael Schulenberg afterward "because he was concerned, and he wanted to do the right thing for his body."

Prince died six days later from an overdose of Fentanyl.

Interestingly, Hill rehearsed with Jackson days before his death -- she famously dueted with him in "This Is It." Dark coincidence, but there's your trivia answer.