Danny Cohen, a distinguished computer scientist who helped develop the first digital visual flight simulator for pilot training, early digital voice conferencing and cloud computing, has died at his home in Palo Alto.

Cohen, who did much of his research at USC, died Aug. 12 at age 81. He was suffering from Parkinson’s disease, his son David said.

Cohen was a graduate student at Harvard University in the late 1960s when he helped develop the first computerized flight simulation system on a general-use computer. The design re-created aircraft flight and the landscape it traveled above.

It was a revelation at a time when easy-to-use home computers didn’t exist and typewriters and rotary phones were still ubiquitous. And it forever changed how airlines trained their pilots.


Before the simulation system, pilots were trained using 3-D replicas, a mechanical design that was expensive and time consuming when having to change out the airport being used for training.

But digitally, “we could switch out JFK and LAX in a fraction of a second,” Cohen told Wired in 2012.

In the mid-1970s, while he was a staff member at USC — where he worked for 20 years at its Marina del Rey Information Sciences Institute — Cohen was approached by the Advanced Research Projects Agency, a government organization that develops new technology for the military.

They asked if he could figure out how to send voice communication through ARPANET, a predecessor to the internet.


“They wanted a secure, fast way to send encrypted messages,” Cohen told Wired. With the help of other researchers from across the country, they designed the first teleconferencing and internet telephony in the late 1970s. By 1978, they held their first conference call.

“He realized that for real-time communication it can be better to lose some data than to have a delay — that is, when you’re doing a Skype call you’d rather hear a little static than have the call stop for a minute and then resume with what your interlocutor said a minute ago,” his son wrote in an email.

In time, this early version of voice-over IP evolved into the ability to send voice and video through cyberspace.

“My dad was making things that he thought were useful, fun and interesting,” he said.


Cohen was born Dec. 9, 1937, in Haifa, Israel, to David, an electrician, and Dorit Ostreicher, the head of an organization that offered support to Israeli soldiers. Cohen’s brother, about 10 years his junior, was born with a congenital heart defect and died as an infant.

Cohen picked up an interest in flying as a boy (eventually becoming a pilot) and became interested in computers in high school after reading a newspaper article on the subject.

As a young man in the mid-1950s, Cohen was a paratrooper in the Israeli Army. In 1963, he earned a bachelor’s degree in mathematics from the Israel Institute of Technology.

He was married in 1961 and later divorced. His second marriage also ended in divorce, but it first bloomed in what was perhaps the earliest online dating courtship.


The year was 1973, and Delia Heilig was working a graveyard shift as a computer operator at the Information Sciences Institute. Cohen had posted a puzzle game in the ARPANET and Heilig submitted her solution.

Cohen was impressed and sought her out — a simple venture at a time when only several dozen computers were connected to the ARPANET, she recalled. He found her and invited her to fly.

In 1965, Cohen moved to the U.S. to study at the Massachusetts Institute of Technology, where he started developing the flight simulator. Years later, he transferred to Harvard University, where he completed the simulator with professor Ivan Sutherland, who invented the Sketchpad computer interface system.

He earned his PhD in 1969 and became a Harvard faculty member soon after. Cohen also taught at UCLA briefly in the late 1970s. He wanted to take scuba diving classes at the campus but was told he needed to be faculty to do so, Heilig recalled. So he signed up to teach a computer science class and, in exchange, learned to scuba dive.


Curious and always the problem solver, Cohen built the first digital libraries for quicker and better information access, worked on an e-commerce project, and created the precursor of today’s cloud-based technology. He also applied the terms Big Endian and Little Endian — taken from Jonathan Swift’s satirical 1726 novel “Gulliver’s Travels” — to computer science in his 1980s article “On Holy Wars and a Plea for Peace,” which analyzes the order of bytes.

Cohen worked at Sun Microsystems Laboratories (which later merged with Oracle) as an engineer for more than 10 years. He retired in 2012 and was inducted into the Internet Hall of Fame that same year.

Heilig recalled her ex-husband as being playfully innovative, spontaneous and fun. “He never drank because he thought there might be a plane in need [of] a pilot,” she said.

And Cohen was a practical joker who over the years published articles under the name Professor J. Finnegan, a fictional co-author, of Oceanview University in Oceanview, Kan.


“Some of those articles were spoofing academic work which he considered to be not worthwhile or not significant,” said Stephen Casner, a friend and retired computer scientist.

When they were both at the USC branchin the mid-1970s, Casner recalled, they’d often drive to the Santa Monica airport and fly to Catalina Island for lunch. “His driving,” he said, “was dangerous, but his flying style was fine.”

His passion to create and test the possibilities of technology, Cohen once said, was this: “Always remember that just because we don’t know how to do it is not a reason for us not to do it.”

He survived by his son, ex-wife and two grandchildren.