5 things to know for April 21: Ceasefire deadline, summer travel, redistricting, Apple, Mexico’s pyramids

Fresh concerns about aviation safety are surfacing this week after another close call in the skies. Two Southwest Airlines jets recently had to take evasive action at Nashville International Airport after collision alarms sounded in the cockpit. Here’s what else you need to know to get up to speed and on with your day.

President Donald Trump pushed the expiration of the truce with Iran to Wednesday evening ET, saying it’s “highly unlikely” he will extend it further if no deal is reached. This gives negotiators an extra 24 hours of talks before Trump must decide whether to follow through on his threat to blow up Iranian bridges and power plants — a possible war crime. Read more.

On top of higher airfares and added fees driven by the war with Iran, airlines in Europe and Asia are now facing a potential jet fuel shortage. This raises the odds of flight cancellations and schedule cuts, spelling trouble for the summer travel season. Read more.

Voters in Virginia will head to the polls today to decide whether to accept or reject a Democratic plan that could dramatically redraw the state’s congressional maps and help shape the midterm elections. Nearly 1.4 million Virginians have already cast early ballots, a sign of unusually high interest for an April special election. Read more.

John Ternus, Apple’s senior vice president of hardware engineering, will become the company’s CEO on September 1. This comes after Tim Cook announced Monday that he will step down following more than a decade spent transforming the company into a $4 trillion behemoth. Read more.

Tim Cook, the executive who led Apple to become a $4 trillion company and defined its identity in the post-Steve Jobs era, is stepping down as CEO, Apple said on Monday. CNN's Clare Duffy reports that John Ternus, Apple’s senior vice president of hardware engineering, will take over as CEO effective September 1. Cook will become executive chairman of Apple’s board of directors and will remain as CEO through the summer to ensure a smooth transition, the company said.

An eyewitness captured the moment a gunman opened fire on a crowd of tourists visiting Mexico’s historic Teotihuacán pyramids on Monday. Authorities say the suspect shot and killed a Canadian woman and injured at least 13 others. Read more.

John Korir, the defending champion, shattered the competition Monday with the fifth-fastest marathon ever. Sharon Lokedi also repeated as champion, winning the women’s race for a second straight year. The coin toss has entered its digital era.

A once large and peaceful group of chimpanzees in Uganda has now split into two, causing a rare “civil war” among the primates. The satirical news site said it has reached an agreement to take over conspiracy theorist Alex Jones’ InfoWars company. Around 60 parents are heading to Capitol Hill this week in a renewed push for online safety laws, hoping to build on the momentum of court wins against social media companies last month.

CNN's Jim Sciutto takes us to northern Alaska for an exclusive look at how the US Army is preparing for the next iteration of arctic warfare. The 11th Airborne are known as the "Arctic Angels", and they are battle testing drones in extreme climates to combat the rising threats posed by adversaries like Russia and China. In this video, CNN’s Jim Sciutto takes you to northern Alaska for an exclusive look at how the US Army is preparing for the next iteration of arctic warfare.

Today’s edition of 5 Things AM was edited and produced by CNN’s Andrew Torgan.