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An aviation photographer took this photo of the missing EgyptAir A320 jet on June 11, 2015.
PHOTO: Courtesy GEWI Fotografie
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PHOTO: Egyptian Armed Forces
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The EgyptAir Airbus A320 registered as SU-GCC is seen here on June 11, 2015.
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Story highlights

Juliette Kayyem: Donald Trump can say it's terrorism with no evidence, but a serious investigation isn't that easy

Security vulnerabilities in aviation are many, but mechanical cause is also possible, she says

Editor’s Note: CNN national security analyst Juliette Kayyem is the author of the best-selling “Security Mom: An Unclassified Guide to Protecting Our Homeland and Your Home.” She is a professor at Harvard’s Kennedy School, a former assistant secretary of Homeland Security in the Obama administration and founder of Kayyem Solutions, a security consulting firm. The opinions expressed in this commentary are hers.

(CNN) —  

EgyptAir Flight 804’s downing is a tragedy. But we still don’t know what kind of tragedy. While Donald Trump’s certainty that it was a terrorist act may assure some, and could even be accurate, this isn’t how investigations like this work. Theories serve only as a way to guide this investigation, but it is facts that will tell us what actually happened. And that matters not simply for the future safety of the global aviation network, but for the stresses on America’s own aviation apparatus.

As data, sometimes conflicting, sometimes simply inaccurate, comes through over the next couple of days, it should be somewhat reassuring to recognize that the potential explanations are limited. Planes do not simply fall from the sky. The most likely theories of the case are that it was either pilot error, mechanical failure, or some purposeful disruption like terrorism.

The data so far suggests any of the theories could be true but certainly there is a possibility that it could have been terrorism.

While no one has claimed responsibility, the confluence of data points – no SOS from the pilots, a plane out of control, no weather explanation, Egypt Air’s suggestion that terror is their more likely theory, the overall threat environment, and a history of airport security lapses at all the plane’s destinations – cannot be ignored. These facts explain why the U.S. government is saying terrorism is its “working theory.” But, again, in the absence of evidence of an explosion, a group claiming responsibility, and any physical evidence, the working theory is only that.

And while finding the debris (and potentially a trace of explosives) is essential to determine which theory proves right, it would not tell us how an attack occurred. A not insignificant number of people had access to this plane in four countries including airport personnel, passengers and flight employees. And that does not even account for the checked luggage.

The magnitude of this investigation is evidence of just how complex our global aviation system is. And that is worth remembering as America’s own security apparatus, the Transportation Security Administration, comes under increasing pressure to speed up delayed travel times.

01:09 - Source: CNN
EgyptAir Flight 804's final moments in 1 minute
An aviation photographer took this photo of the missing EgyptAir A320 jet on June 11, 2015.
PHOTO: Courtesy GEWI Fotografie
An aviation photographer took this photo of the missing EgyptAir A320 jet on June 11, 2015.
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PHOTO: Getty Images
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A relative of a passenger who was flying aboard an EgyptAir plane that vanished from radar in route from Paris to Cairo overnight cries as family members are transported by bus to a gathering point at Cairo airport on May 19.
PHOTO: KHALED DESOUKI/AFP/Getty Images
A relative of a passenger who was flying aboard an EgyptAir plane that vanished from radar in route from Paris to Cairo overnight cries as family members are transported by bus to a gathering point at Cairo airport on May 19.
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PHOTO: Egyptian Armed Forces
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PHOTO: Egyptian Armed Forces
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PHOTO: Egyptian Armed Forces
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This August 2015 photo shows EgyptAir Airbus A320 with the registration SU-GCC taking off from Vienna International Airport in Austria.
PHOTO: Thomas Ranner/AP/FILE
This August 2015 photo shows EgyptAir Airbus A320 with the registration SU-GCC taking off from Vienna International Airport in Austria.
Now playing
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A relative of a passenger who was flying aboard an EgyptAir plane that vanished from radar in route from Paris to Cairo overnight cries as family members are transported by bus to a gathering point at Cairo airport on May 19.
PHOTO: KHALED DESOUKI/AFP/Getty Images
A relative of a passenger who was flying aboard an EgyptAir plane that vanished from radar in route from Paris to Cairo overnight cries as family members are transported by bus to a gathering point at Cairo airport on May 19.
Now playing
01:46
U.S. officials believe EgyptAir brought down by bomb
The EgyptAir Airbus A320 registered as SU-GCC is seen here on June 11, 2015.
PHOTO: courtesy GEWI Fotografie
The EgyptAir Airbus A320 registered as SU-GCC is seen here on June 11, 2015.
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Wednesday, I wrote a piece for CNN Opinion regarding the controversies surrounding long delay times at domestic airplanes. It seems almost moot now, but shouldn’t be.