On January 11, 1933 Sir Charles Kingsford Smith and his crew used Gerroa’s Seven Mile Beach as the take-off point for a flight to New Plymouth, New Zealand.

On board was a special batch of cargo - several envelopes postmarked January 10, the day before Kingsford Smith’s Seven Mile beach take-off, and signed by crew and passengers.

Known as airmail cover, and carried on historic flights, only five of the valuable collector's items are thought to exist - with one housed in Gerringong’s History Museum.

The letter, carried by “Smithy” and signed by three crew and two passengers, thanked the town’s local ladies for providing a box of peaches to the aviator and his crew before their sandy launch.

“This event established the first airmail route between Australia and New Zealand and was certainly a significant part of our local history,” says Gerringong Historical Society secretary Joy Fullager.

Joy says the airmail cover, sourced by South Coast stamp collector John Graham and donated to the museum two years ago to mark the 90th anniversary of the historic flight, was a welcome addition to GLaM’s dedicated Charles Kingsford Smith collection.

“People who visit the Gerringong Heritage Museum are always very interested in the items related to Charles Kingsford Smith,” she says.

“The museum has a video with footage of Charles Kingsford Smith landing on Seven Mile Beach in 1933, which is very popular with visitors.

“The video’s commentary is by Gerringong’s Clive Emery, who watched the historic flight when he was a child.”

Just two years after the famous aviator’s take-off from Gerroa to NZ, Kingsford Smith and co-pilot Tommy Pethybridge went missing on November 8, 1935 while attempting to break the flight speed record between England and Australia.

The final resting place of the pilot, crew, and plane has baffled historians for generations.

Now to mark the 90th anniversary of the disappearance of Kingsford Smith aboard his legendary Lockheed Altair 8D aircraft, Lady Southern Cross, award-winning Australian writer, filmmaker, and explorer Damien Lay has released his book Of Air and Men.

Lay is considered one of the world's leading authorities on the disappearance of the Lady Southern Cross and has spent more than two decades researching and documenting the historic event.

Of Air and Men not only tells the story of the famed aviator - the first person to circumnavigate the globe and one of the greatest long-distance flyers in history - but documents Lay’s quest to find his final resting place and the impact Kingsford Smith’s disappearance had on his family.

The wreckage of the Lady Southern Cross was first discovered in 2009, off the Burmese coast, using sonar imaging.

Three years and 18 dive expeditions later Lay and his team had recovered more than 40 pieces from the wreck.

Charles Kingsford Smith.

Many of the dives were over 100 feet in depth in treacherous conditions - not least due to the political turmoil in Myanmar and the threat posed by pirates.

“We were diving in the most dangerous conditions on earth,” Lay recalls. “Strong currents, near-zero visibility, political turmoil, pirates, militias, we had no medical evacuation, no safety net. Just determination.”

The wreckage found by Lay and his team included timber and fuel lines and the discovery made the modern-day explorer even more determined to “one day … bring the men of the Lady Southern Cross home”.

Over the past 20 years, Lay has worked closely with the aviator's son, Charles Arthur Kingsford Smith, who has lived in the US since he was five, as well as the wider Kingsford Smith family, and the Pethybridge family.

The book uses historical fiction to document the aviation legend’s life, the mystery surrounding his final flight, and the impact of his disappearance on his family, including his son who was just a toddler at the time.

“I have only a few snatches of memory of my father, and I would have greatly enjoyed his love and fellowship growing up but his disappearance just before my third birthday sadly ended that possibility," says the now 92-year-old Kingsford Smith junior.

“Adding to the sadness is the frustration that much is unknown about what happened, so we really can't close the book on his life story.

"Many have offered theories and speculation about what happened.

“Damien dedicated years of his life, at vast expense, in searching the area where the plane almost certainly went down, resulting in the most likely theory of what really happened to my father in the Andaman Sea."

Of Air and Men is available through Amazon, Booktopia and many independent Australian booksellers.

A copy of the book has been donated to the museum, which also houses a model of Kingsford Smith’s Southern Cross and photos from his time in the region.

“The Gerringong Historical Society is very appreciative for its copy of the book which has been added to our library,” says Joy.

The museum, which is staffed by community volunteers, is open on Fridays and Saturdays from 11am-3pm.