Who are the missing UK girls thought to be in Syria?

(CNN)In airport surveillance pictures, the three young women look like typical travelers. But their destination was anything but ordinary.

British police announced last week that three east London classmates -- Shamima Begum, 15; Kadiza Sultana, 16; and Amira Abase, 15 -- had flown aboard a Turkish Airlines plane from London's Gatwick Airport to Istanbul on February 17.

From there, they wanted to go to Syria with the apparent goal of joining ISIS. On Tuesday, authorities said they believe the three girls have made it to their target country.

British Prime Minister David Cameron has said the case highlights the need to fight ISIS on multiple fronts.

"It does make a broader point, which is the fight against Islamist terror is not just one that we can wage by the police and border control," he said.

"It needs every school, every university, every college, every community to recognize they have a role to play, we all have a role to play in stopping people from having their minds poisoned by this appalling death cult."

Here's a closer look at three teens and their families:

Shamima Begum

Shamima Begum

Shamima's family released a statement through London's Metropolitan Police, begging the girl to reach out and reconsider.

"Syria is a dangerous place, and we don't want you to go there. Get in touch with the police, and they will help to bring you home. You are not in any trouble."

The family said it understands that Shamima has strong feelings about wanting to help those she believes are suffering in Syria.

"You can help from home, you don't have to put yourself in danger," the statement reads. "Please don't cross the border. Please come home to us. Our Mum needs you home and is really worried. We are not mad at you, we love you."

Shamima's sister, Renu Begum, described the 15-year-old as an "A-star student." But even bright, promising children can fall prey.

"To convince such young girls at that age that are so vulnerable ... it's just wrong," Begum said. "It's a really evil thing to do. You're breaking up entire families."

Kadiza Sultana

Kadiza Sultana

Kadiza's sister, Halima Khanom, spoke to the BBC.

She said everyone in her family is hurting and wants to know whether Kadiza is safe.

"We want you to know that we all miss you and we love you," Khanom said in a video message directed at her sister.

"Find the courage in your heart to contact us and let us know that you're safe and you're OK. That is all we ask of you."

Amira Abase

Amira Abase

Amira Abase told her father that she was going to a wedding. Her family reported her missing when she did not return.

"What she's doing is completely nonsense," Amira's father, Abase Hussen, said.

He implored Amira to come home.

"Remember how we love you. Your sister, brother, they cannot stop crying."

Separately, Hussen spoke to the BBC.

While holding a teddy bear that Amira had given her mother for Mother's Day, he said his daughter had never expressed an interest in ISIS.

"The message we have for Amira is to get back home. We miss you," Hussen told the BBC. "Please think twice."