Born in 1910, he was a bit of a hooligan, but reformed in military school - eventually getting in to Yale where he studied drama and got some work in the film industry. He was making a documentary in the Rhineland when Hitler invaded, and Gann narrowly escaped the Nazi troops. Back in the US, he purchased a half-share in an aircraft with Burgess Meredith (!) and got his pilot's license.
During the Depression, Gann moved to California - and then back to New York - where he provided for his family with odd jobs flying and a bit of writing on the side. When World War II broke out, Gann volunteered, and flew cargo flights in all around the world, including the dangerous (and storied) 'The Hump' airlifts into China.
After the war, he returned to the West Coast, where he continued to fly, as well as indulge his love of sailing. His family life was fraught with problems and tragedies, but by the late 1960's, he was happily remarried and living in Washington State, where he continued to write - and act as a vocal advocate for local conservation efforts. He flew his last flight in 1991 - celebrating the 50th anniversary of being a captain for American Airlines - and passed away shortly after.
Also, according to Wikipedia, despite his prolific writing output (over two dozen novels - ten of which were made into films), Gann struggled with writer's block a lot - and used to chain himself to his desk. Literally.
Gann's fiction largely focused on the worlds of air and sea, as he tried to capture the danger and excitement of his passions in words. Twilight for the Gods (1958) is a particularly mournful book, as it takes place one of the last sailboats in the Pacific - the crumbling Cannibal. The boat is held together largely by strength of will, most of that coming from its captain, Bell. The cargo is second-rate, Bell's fellow officers are grumbling and useless, the crew are has-beens and never-will-be's and even the passengers are all failures in their own unique ways. When this 'routine' journey becomes a disaster, it becomes all too easy for them to lose hope. And yet, in the face of this primordial battle - man vs nature, a ship vs the elements - they all achieve a sort of greatness.
Twilight praises the era of sail, and the notion that intuition, gumption and willpower are being replaced by cold mechanics and colder hearts. By nature, this is nostalgic, but Gann's book is less about mourning the changes than eulogising the past. The new boats are better - safer, faster, more efficient - but he asks the reader to spare a moment in recognising, and respecting, those that went before, and made their living in the dangerous, slow, and scary days.
For a short book, and one packed with disaster, Twilight is also, well... slow - containing a density that captures the length and tension of the Cannibal's journey. This meandering pace is reflected in Gann's characters - many of whom are taking advantage of the sea voyage to reconsider each and every one of their life decisions. Their communal angst becomes slightly wearying, and it is hard not to cheer for the onset of disaster, if only to get them to stop thinking for a moment. Tellingly, the most compelling relationships in Twilight aren't entirely human: Bell's "marriage" to the Cannibal is a surprisingly powerful romance, containing all the blindness and passion of the truly lovestruck. And its odd mirror, in Bell and his dog Anchor, is equally poignant.
For a book with a similar theme, The High & The Mighty (1952) is anything but slow. In this, earlier, novel, Gann's writing about air travel, and the action takes place on a flight between Hawaii and San Francisco. Gann labours the detail, describing the many processes and checks and gears and switches and fail-safes and bits and bobs that all go into 'modern' air travel - but that's all in support of his theme. Again, no system is safe from disaster, and when complex systems fail, it comes down to intuition, gumption and willpower. Mechanics can take you so far; it takes humanity to provide everything else. Like Arthur Hailey's Airport, this is a masterful look at systems and their collapse.
Unlike Twilight, The High & The Mighty is about the best of everything - the top pilots, the classiest crew and the richest, most successful air passengers. It is about a system with everything working in its favour, as opposed to the poor Cannibal, where all the odds are stacked against it. The High is also a much faster book, there's a physical and notional 'point of no return', where everything kicks off - and quickly.
However, if anything, The High feels slightly less tense than Twilight, possibly because air travel is now so familiar (unlike travelling by sail), and the 1950s version of air travel feels almost ridiculously old-fashioned. With Twilight, the disaster is so 'alien' that Gann's detail works to build the world and suspend disbelief. With The High, it is harder - little moments like the smoking on planes, the ticket buying process, the absence of security (someone walks on with a gun!) and the institutional sexism of the stewardesses - when I know this has all changed, it makes it harder to grow absorbed in the rest. But as a snapshot of a world just-passed-by, this is excellent.