One of the attackers at Istanbul's Ataturk airport blew himself up outside, giving the other two the opportunity to get inside the terminal, Turkey's prime minister has said.
The suicide attackers, armed with guns and bombs, killed 42 people and left dozens more injured in a terror assault blamed on Islamic State (IS).
PM Binali Yildirim said: "When the terrorists couldn't pass the regular security system, when they couldn't pass the scanners, police and security controls, they returned and took their weapons out of their suitcases and opened fire at random at the security check.
"One blew himself up outside and the other two took advantage of the panic created during the shoot-out and got inside and blew themselves up."
Travellers and airport workers described scenes of chaos as gunfire and explosions sent crowds fleeing in terror on Tuesday night.
Airport surveillance video posted on social media shows the moment of one explosion, a ball of fire that sent terrified passengers racing for safety, while another shows an attacker felled by a gunshot from a security officer blowing himself up seconds later.
The victims included at least 23 Turkish citizens and 13 foreigners, and the Istanbul governor's office said more than 230 people had been injured.
IS has not yet claimed responsibility for the attack, although it did issue an infographic celebrating two years since announcing a caliphate. It claimed to have "covert units" in Turkey, among other places.
Funerals for some of the victims began as Turkish authorities continued to try to piece together how the attack happened, going through surveillance footage and interviewing witnesses to establish a preliminary timeline.
As dawn broke over the destroyed terminal, workers began removing debris from the blast. The airport reopened on Wednesday morning, though flights were subject to cancellation and delay.
Mr Yildirim said it appeared that the IS group, also known as Daesh, which has threatened Turkey repeatedly, was responsible.
"Even though the indications suggest Daesh, our investigations are continuing," he said.
He also suggested the attack could be linked to steps Ankara took on Monday towards mending strained ties with Israel and Russia.
He called for national unity and "global co-operation" in combating terrorism.
"This has shown once again that terrorism is a global threat," Mr Yildirim said. "This is a heinous planned attack that targeted innocent people."
US President Barack Obama pledged to dismantle "organisations of hate" after the bombing.
He said the gun and bomb attacks show how little these "vicious organisations" have to offer.
Mr Obama offered his condolences to the Turkish people, and has spoken with Turkish President Recep Tayyip Erdogan.
Earlier, Russian President Vladimir Putin expressed condolences for the Istanbul attack, and sought to begin a process of improving relations with Turkey.
Belgian PM Charles Michel said on Twitter: "Our thoughts are with the victims of the attacks at Istanbul's airport. We condemn these atrocious acts of violence."