The slow buildup is officially over on AMC’s new companion Web series, “Fear the Walking Dead: Flight 462,” now that part 5 has been released early on the official AMC mobile app. The passengers are about to complete their journey when things on the ground and in the air take a turn for the worse.

Last week’s episode saw a clearly very infected passenger succumb to a coughing fit and make his way to the plane’s restroom. His wife tried to explain that it was an ordinary sickness, but none of the other passengers were really buying it. In the most recent installment, a great deal of time has apparently passed as the passengers are making their descent into Phoenix. As the flight is coming to an end, one passenger has apparently been impatiently waiting to use the bathroom. She asks the flight attendant to allow her to use the first-class stall, but apparently that’s against the rules. The flight attendant ends up banging on the stall door calling out to the unresponsive man inside to take his seat before they begin to land.

While the commotion is going on in back of the plane, the boy that opened the series looks out the window to see half of Phoenix go dark. It’s unclear exactly what makes the power go out, but odds are good it has something to do with the zombie apocalypse raging in full swing down below. As several passengers begin to panic, the brief webisode ends. Although it seems like unrest is about to consume the tiny plane’s cabin once a walker jumps out of the bathroom, there are still 11 installments left before the “Flight 462” storyline concludes. It’s surprising the plane made its way to Phoenix given that it’s been announced that one surviving character on “Flight 462” will be joining the cast of “Fear the Walking Dead” in Season 2. That show takes place in Los Angeles, meaning the plane -- or passenger -- will have to get back there somehow.

So, to put it like a difficult math problem: If Flight 462 cannot land due to a power outage in Arizona, how long can the passengers last with a walker on board before the pilot turns the aircraft around and heads back to California?

Fans can view episode 5 of “Fear the Walking Dead: Flight 462” on any Android, iOS or Windows smartphone by downloading the AMC app. Those who don’t have access to the app can wait until Sunday when the Web short will premiere during a commercial break for “The Walking Dead” Season 6, episode 5. It will be available on the AMC website for “Fear the Walking Dead” immediately after.

What do you think of “Fear the Walking Dead: Flight 462” so far? Comment below or tweet your thoughts to @TylerMcCarthy.