How did the Istanbul airport attackers get past security?

Istanbul airport has numerous security measures
turkey airport sercurity ivan watson bpr nr_00002820

    JUST WATCHED

    Istanbul airport has numerous security measures

MUST WATCH

Istanbul airport has numerous security measures 01:01

Story highlights

  • Ataturk Airport has two layers of X-ray security screenings
  • In addition to the screenings, it has a vehicle checkpoint outside the airport compound
  • Two attackers are believed to have entered via the arrivals hall

(CNN)The deadly assault by three suicide bombers on Istanbul's Ataturk Airport once again shows the difficulty in averting terror attacks.

Terrorists targeted the 11th busiest airport in the world in a country that borders the ISIS-stronghold Syria, and it's not hard to see why Ataturk posed an attractive soft target.
But what's particularly unnerving about the latest incident is the regional aviation hub had a much tighter security system in place than many other airports.
Travelers using the airport are required to undergo double security screenings. One before they enter the international terminal building, and a second time after they go through passport control.
It also stationed a vehicle checkpoint about 500 meters from the entrance of the international terminal -- although only suspicious vehicles are stopped and checked.
So how did the attackers get through unleashing violence on innocent, unsuspecting crowds?

Weaker security in arrivals

The international arrivals hall is an area with weaknesses the attackers may have exploited, CNN's Senior International Correspondent Clarissa Ward reports.
"There's heavy security at the entrance to the international departures hall," Ward said. "There's a full screening process. You have an X-ray machine and you have to go through a metal detector. But in the arrivals hall, of course you don't have that same level of security, so two of the attackers we believe went into the arrival halls."
People going to the arrivals section on the bottom floor are required to go through metal detectors but are overseen only by a light guard presence.
The third bomber meanwhile detonated at the car park, outside the first X-ray security screening point. It's unclear whether the attacker's original intent was to set off an explosion there but it raises another issue in airport security.
Authorities can create and bolster checks that prevent 9/11 style attacks where terrorists board and take control of planes, but attackers can adjust their targets to areas before the screening process begins.
Bob Baer, a former CIA intelligence officer who specializes in Middle East security issues, said there is no foolproof way to preventing a similar airport attack.
"You cannot protect these airports 100% ... especially in a place like Turkey, where ISIS has cells everywhere," he said.

Security staff response

What about the response from Turkish airport security as the tragedy unfolded?
Harrowing surveillance footage shows what appears to be a Turkish security personnel officer shooting one of the attackers. The attacker falls to the ground and drops a gun that slides across the floor. The personnel approaches but seeming to realize the imminent danger, runs away just seconds before the attacker detonates.
Istanbul Ataturk Airport

-- 11th busiest airport in the world (2015)

-- Europe's third busiest airport (2015)

-- ~62 million passengers passed last year

-- There are two main passenger terminals

-- Terminal 1: older, smaller, domestic

-- Terminal 2: newer, bigger, international

-- Vehicle checkpoint at compound entrance

-- X-ray checkpoint at terminal entrance

-- The airport is roughly 15 miles from the city

Source: Airports Council International/CNN

Witnesses said the response to the threat seemed swift.
As the attack was ongoing and it was unclear how many bombers there were, security staff escorted people deeper inside the airport to the gates, past the second X-ray scan point, where they would be safer.
Mine Iyidinc said they led her and others hiding in a shop to a safe zone near gate 224.
Iyidinc stayed there for about four hours, during which she heard an explosion coming from another section of the airport, she told CNN.
"It was like a hell. There was a panic everywhere ... I did not see any dead bodies after leaving the safe area but there was a lot of blood everywhere," Iyindinc said.
"The security staff did their job as it should be done," she added.
Traveler Fatos Karahasan, who also witnessed the bloodshed, said he was shocked that such an attack could occur at Ataturk.
"I do not think the police were not doing their jobs. Yet, it was a meat market. A scene dominated by the silence of death."