An autopsy has deteremined that the 61-year-old California woman found dead in the restroom of a Delta Air Lines jet that landed in Atlanta Wednesday morning died from a heart abnormality.

According to Dr. Kris Sperry, Georgia's chief medical examiner, a pre-existing heart condition was responsible for Michaele O'Neil Carnahan's sudden death.

According to a GBI statement released Thursday afternoon, Carnahan was being evaluated by her personal physician for suspected heart problems. The specific nature of the heart disease will be determined later after further examination of the heart.

The crew noticed the restroom was occupied as Flight 950 from Los Angeles made a final approach to land at 5:51 a.m., Delta spokeswoman Keyra Johnson said. Delta officials have not said how long Carnahan, may have been in the restroom.

"Upon final approach into Atlanta, our inflight crew was advised that a passenger passed away in the on-board restroom," Johnson said. "Medical professionals and authorities met the flight."

John Bankhead, spokesman for the Georgia Bureau of Investigation, said Carnahan was on her way from her home in Ventura, Calif., to Florida for a wedding.

Atlanta police stationed at Hartsfield-Jackson International Airport, the world's busiest, respond to calls about dead bodies on airplanes a couple of times a year, said spokesman Eric Schwartz.

An exact tally of in-flight deaths is hard to determine. According to the Federal Aviation Administration, which is responsible for safety regulations and mechanical issues involving planes, airlines are not required to track or report the medical incidents they handle.

MedAire, an Arizona-based company that staffs doctors on the ground to advise flight crews in a medical emergency, counted 89 deaths for the flights they handled in 2006, which represents about one-third of the world's commercial flights.

The Associated Press reported in February this year that an American Airlines passenger returning home to Brooklyn from Haiti died after complaining she couldn't breathe.

In November 2007, a passenger reportedly died aboard an American Airlines flight into Chicago after suffering an arterial blockage. Roger Roth of Topeka, Kan. was found unconscious in an aisle seat on American Airlines flight 1592 from Kansas City, Mo., to Chicago.

In April 2007, the Associated Press reported that a passenger died in the restroom during an American Airlines flight and wasn't found until the cleaning crew boarded the plane after it landed, according to a federal lawsuit.

Taisuke Matsuo apparently had a fatal heart attack after he went to the restroom during a flight from Tokyo to Chicago during the first leg of a trip home to Indianapolis.

Meanwhile, Johnson said "our condolences go out to the [Carnahan] family."

AJC staff writers Mike Morris and Jose Pagliery and news researcher Richard Hallman contributed to this story.