'Grey's Anatomy' Season 11 Spoilers: Episode 20 'One Flight Down' Recap

This week on "Grey's Anatomy," a plane crash rocks Grey-Sloane Memorial to its core, and Meredith struggles through the day as she waits to hear from Derek, who appears to be missing.

In "One Flight Down," Meredith is worried about Derek since he never made it to his big meeting at the White House and no one has seen him since he left the house to go to the airport. Later, a small plane crashes, and this brings about bad memories for Meredith and Arizona, who were in a plane crash before — the plane crash which killed Dr. Mark Sloane and Meredith's sister, Lexie.

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Meredith tries to help the victims of the plane crash, but soon she realizes that she can't do it as it now appears that she's suffering from post-traumatic stress disorder. She looks for Arizona and finds her sitting on the floor of the supply room. Meredith joins her, and they assure each other that they're OK.

In another part of the hospital, Alex tells Callie that they ought to watch Meredith and Arizona carefully and that maybe they shouldn't be treating the plane crash victims. Callie agrees to that, but says that she'll look after Meredith since she can't be "that person" for her ex-wife anymore.

At the end of the day, Alex told Arizona that when their plane crashed, he was the one who amputated her leg because he was running out of time to save her. It was Callie's decision, but he was the one who made the cut.

Arizona immediately runs to Callie and demanded to know why she never told her about it. "Why didn't you tell me about Alex and my leg? All this time, you let me hold it against you. Why?"

Callie tells her, "I made the call. No matter what, it was still me making the call to take your leg and I knew you were going to hate me. I didn't want you to hate Alex too. I wanted you to have somebody."

Meanwhile, Meredith is inundated with flashbacks from the plane crash while also remembering what Derek told her before he left for D.C.

Derek told her that he's back for good and promised that he'd never leave again. He also told her that he wants more kids.

"It's always been you. But I want more of this, of us. I want to have more. Let's have more," he said.

Everyone in the hospital is trying to help Meredith, and Bailey comes up with the perfect solution. She tells Meredith that she has until 5pm to hear from Derek. If it gets to 5 p.m. and she doesn't hear from him, then she can start to panic. Meredith thinks that it's a good idea and focuses on the task at hand.

Back at her home, Meredith sits on the couch and checks the time. At 5pm, she gets up to call the authorities about her missing husband when a car pulls up on her driveway, and the blue and red lights of a police car reflect in the window that Meredith is looking through.

"Grey's Anatomy" airs on Thursdays at 8/7c on ABC.