Editor in London Sees Tweet Des Shoe, a digital editor in London, spots a tweet about smoke at the Brussels Airport. She alerts Michael Wolgelenter, another London editor, who in turn contacts Alissa Rubin, The Times’s Paris bureau chief.

(Ms. Rubin and Aurelien Breeden, a reporter from the Paris bureau, were in Brussels to cover the arrest of Salah Abdeslam.) ‘Sheer Dumb Luck’ — Paris Bureau Chief on Site Ms. Rubin was scheduled to return to Paris the night before, but she missed the last train and happens to be in a hotel in Central Brussels when the London bureau emails: “There are reports of explosions at the Brussels Airport.” First Article Drafted Mr. Wolgelenter writes an article (“By The New York Times”) citing social media and TV reports; Diego Sorbara, the chief of the London copy desk, starts work on a headline. Article Posted on NYTimes.com The Times’s home page includes mention of the attack — but only a small one, because its extent remains unclear. Times Terror Team Alerted Mr. Wolgelenter emails a group that was originally created for the Paris attacks: “blasts at Brussels Airport.” The group consists of 129 people — reporters, editors, picture editors and others around the world who were involved in The Times’s coverage of the Paris attacks in November. First Article Filed From the Scene Ms. Rubin files her first article, datelined Brussels. Confusion Reigns Ms. Rubin emails: “Most people do not seem to know anything.” Reporters Dispatched to Brussels Sewell Chan, the international news editor in the London office, emails Richard Stevenson, who runs The Times’s Europe operations, suggesting that Dan Bilefsky and Kimiko de Freytas-Tamura, two reporters based in London, be dispatched to Brussels. Paris Bureau Chief Emails: ‘One Dead’ Ms. Rubin says that the Belgian news agency is reporting one dead; The Associated Press follows suit a few minutes later, which The Times reports. Aviation Reporter on the Job Nicola Clark, a reporter in Paris who covers aviation, is on the case, making calls about the Brussels Airport and airport security in general. Tweet: ‘2 Explosions Bring Brussels Airport to a Halt’ Laurie Kawakami, who is running The Times’s social media accounts from Hawaii, publishes the first Times tweet about the attacks: “2 explosions bring Brussels airport to a halt.”

(She hands off to Claire Barthelemy, who just the day before started a new role as the London newsroom’s social media editor. Ms. Barthelemy keeps up a stream of news updates on the attacks during the European day.) ‘TV — Blasts’ Adam Nossiter, a Paris-based correspondent, sends an email (subject line: “tv — blasts”) summarizing the news from BFM, a French network and website that Mr. Nossiter, who is fluent in French, has been monitoring. System Architecture Built Chris Stanford, a digital editor in London, creates the system architecture so The Times can run a blog. Feed on Belgian Media Mr. Bilefsky, also fluent in French, sends a feed summarizing news reports in the Belgian media. Station Identified Ms. de Freytas-Tamura reports that the explosion occurred at a station close to the European Union; Liz Alderman, the chief European business correspondent, soon identifies the site as Maelbeek Station. Vacation: Canceled James Kanter, The Times’s Brussels correspondent, receives a call from Mr. Wolgelenter about the attacks. Mr. Kanter abandons his vacation plans and heads to the scene. (No taxis are available; he jogs to Maelbeek Station.) Former Intern Enlisted The Times’s London bureau contacts Milan Schreuer, a former intern from Belgium. Brussels Attack Leads the News The Brussels article moves to the top of the home page and the mobile apps. Station Confirmed Ms. Rubin confirms the explosion at Maelbeek subway station, citing a Twitter post from the Belgian transit authorities. First Photos From the Scene The first few syndicated photographs come in — basic wide shots of the airport. More ‘Sheer Dumb Luck’ Anita Raghavan, a Times freelancer, happens to be in the Sheraton hotel at the Brussels Airport and sends witness accounts from the scene:

“They have been bringing people with slight injuries — bandages around their head, their hands etc — in stretchers into two conference rooms on the first floor. I interviewed a couple people. Please feel free to use these interviews in any coverage today.”

“Also, the first two people I interviewed seemed to indicate that this was near the Delta airlines counter but the last woman was very certain that it was counter 10 for Ethihad (ck spelling).”

“I am low on battery so am just sending you what I have. I will also forward you some video from this guy Jerome in a separate email.”

Ms. Raghavan, who was at the hotel to attend a conference of fraud examiners, was the first Times journalist to provide quotes and accounts from witnesses of the airport attack. The hotel where she was staying was quickly transformed into a triage center for bloodied survivors. ‘Explosions at the Brussels Airport Have Killed at Least One Person’ The Times sends its first news alert — on mobile, email and the web. Cell Networks Overloaded Ms. Rubin and Mr. Breeden email to say that the load on cellular networks is so high that it’s almost impossible to make or receive calls.

Since trains aren’t running, Mr. Breeden heads to Maelbeek Station on foot. 13 Reported Dead, No Confirmation Ms. Rubin emails that many media outlets are reporting 13 dead, but that she cannot get independent confirmation. About 30 minutes later, The Times posts an article saying 13 are dead at the airport, and 15 in the subway station, but attributes it to news agencies. ‘Some Thoughts’ Mr. Chan sends an update to the email list:

“We're following Twitter extremely closely, and using a tool called Dataminr that culls the most significant tweets, for purposes of feeding the live blog. This includes the Brussels transport agencies and every verified account of top Belgian officials.”

“As much as possible, our reporting efforts should focus on trying to get eyewitness accounts, and eventually a detailed chronology of what happened. James is en route to the Maelbeek station.”

Graphic Photos Mona Boshnaq, a picture editor in London, finds three images via Facebook taken by Ketevan Kardava, a Georgian broadcaster.

Questions arise: Are the photos too graphic? Are they invasive of the subject’s privacy? Producers in London weigh in and decide to post one of the photos on the home page.

The image that was originally published was a different frame from the one shown here; the victim on the right was looking straight into the camera.

It was later swapped with this image after a discussion, at the morning news meeting in New York, between Mark Bulik, the editor running the digital news desk, and Michelle McNally, The Times’s picture editor. Video on Deck Hannah Olivennes, a digital assistant in London, begins searching for syndicated video of the bombings. The first Times video depicts evacuation scenes from the Brussels Airport.

Turner Cowles, a video journalist on an early shift in New York, later produced the haunting and now-ubiquitous footage — that a witness shot and shared on Twitter — of a child wailing in a dark subway tunnel. Crisis Meeting Lilia Blaise, a correspondent in the Paris bureau, reports that French leaders have called a crisis meeting. Blog Goes Live: ‘Blood Everywhere’ The Times’s blog on the Brussels attacks — edited by Lillie Dremeaux, deputy digital editor — goes live with five posts, including a quote from Zach Mouzoun, who arrived on a flight from Geneva about 10 minutes before the first blast:

“It was atrocious. The ceilings collapsed. There was blood everywhere, injured people, bags everywhere.”

The blog — a format often used by The Times to cover developing stories — is updated with posts throughout the day, both by journalists on the scene and by writers and editors from afar. Photographer Dispatched to Brussels After calling picture editors in London and Hong Kong, David Furst, the international picture editor, dispatches Daniel Berehulak, a Times photographer, to Belgium. Mr. Berehulak will travel by air from Barcelona via Dusseldorf, and then by car to Brussels. Business Editor Enlisted Prashant Rao, a deputy European business editor, is enlisted to help gather, write and edit blog posts. From Beirut: ‘Please keep an eye on ISIS social media’ Anne Barnard, the Beirut bureau chief, emails The Times’s Syria team — a network of staff correspondents and local bureau staff members, based in the Middle East, who specialize in ISIS-related coverage — to ask that they focus their attention on social media:

“Please keep an eye on ISIS social media for any responsibility claims or other info, and send to Alissa Rubin in Paris (cc’d here). Alissa, our colleague Maher [Samaan], who is on this thread, is in Paris if you need an Arabic speaker ... ” New York Gets the News Clifford Levy, an assistant masthead editor who oversees The Times’s digital platforms, emails The Times’s executive editor, Dean Baquet, and the deputy executive editor, Susan Chira, to alert them of the attacks:

“Scrambling reporters editors and reporters in NYC to help London. Live blog, etc.” Graphics on Deck Patrick Smith, a graphics editor in Paris, draws a map showing the site of the two attacks. 13 Killed and the Toll Could Rise The Times issues its second news alert: “At least 13 people have been killed in explosions at the airport and a subway station in Brussels. The toll could rise.” ‘Staffing Note’ Mr. Wolgelenter sends a staffing update:

“Alissa Rubin, Aurelien Breeden and James Kanter are in Brussels. Kimiko de Freytas-Tamura and Dan Bilefsky are on the way (though getting there won’t be quick). Nicola Clark is making calls from Paris. We are also getting significant help from Anita Raghavan, a freelancer who has worked for the WSJ.” Focus: Live Blog In New York, Patrick LaForge, the editor of the express team (The Times’s breaking news unit), emails Mr. Levy to put the whole team at the live blog’s disposal. Mike McPhate, a member of the team, begins writing for the live blog. He is soon joined by Katie Rogers, Daniel Victor, Victoria Shannon and several others. Slide Show: Live A slide show publishes on The Times’s home page. Coverage Takes Shape Mr. Stevenson, the Europe editor, outlines his plan for the day’s Brussels stories. Executive Editor Sends Signal “Assuming all set up so will stay out of your hair,” Mr. Baquet writes to Mr. Levy. ‘Live Blog Up and Humming’ Mr. Levy replies to the executive editor, Mr. Baquet, and the deputy executive editor, Ms. Chira: “We’re in good shape so far.” Suicide Attack Confirmed Ms. Rubin emails: Belgian prosecutors confirm at least one suicide attacker. Coverage of the Victims Jodi Rudoren, deputy international editor, gets on an earlier train than usual from New Jersey and spends the ride emailing colleagues about graphics, storylines and a plan for profiling each victim.

Palko Karasz, a digital assistant in London, begins work on a list of past attacks in Belgium. Moscow Files Neil MacFarquhar, the Moscow bureau chief, files a short article with reaction from Moscow. Social Media Reporting Russell Goldman, a senior staff editor, searches social media for information about the victims. Graphics Reports Archie Tse, The Times’s deputy graphics editor, reports that the graphics team is “working on a map for the story and maps+photos page with more detail on what happened at each location.”

The package is soon published — and is updated throughout the day. Shifting Coverage The Times scales back its planned coverage on President Obama’s trip to Cuba and slows down the rollout on the Cuba live blog. Second Photographer Dispatched Pierre Terdjman, from Paris, is dispatched to Belgium. ‘What We Know and Don’t Know’ A summary article that will be widely shared all day, “Brussels Attacks: What We Know and Don't Know,” by Ms. Shannon, is first published. She continues to update it through the day; it eventually reaches nearly a million readers. ‘Follow our journalists’ Mr. Chan relays, via Twitter, the accounts for Times journalists who are on the ground in Brussels and Paris. His tweet is retweeted by The Times’s main account. Report From Washington Mark Mazzetti, a Times correspondent based in Washington who covers intelligence, forwards a statement from a ranking member of the Senate Intelligence Committee. Researching the Victims Ms. Rogers and Mr. Victor of the express team are detached by Mr. LaForge — at the request of Kim Fararo, a day editor on the international desk — to help Mr. Goldman of the international desk scour social media and make phone calls seeking information about the victims. Reporting on the Mayor of Brussels Mr. Breeden files a report on a news conference given by Mayor Yvan Mayeur of Brussels:

“He said that there were ‘probably about 20 deaths’ at the Maelbeek metro station but that the situation was still fluid and that toll could change.”

“ ‘The situation in the metro is extremely chaotic,’ he said. ‘Forensic police has lots of work ahead to identify the victims. It will be a long and difficult work.’ ”

“He said that there were many wounded, 106 so far: 17 seriously, 23 who were ‘greatly affected’ by the explosion, and 66 people who were wounded more lightly.”

“ ‘This is clearly an attack against our values of liberty and democracy, against the humanism that we support loudly and clearly in this city of Brussels,’ he said.”

Setting the Agenda At the daily morning news meeting, editors map out the daylong strategy on news from Brussels and elsewhere. The politics team plans a report on the candidates’ response to the attacks, which is published later in the day: “Presidential Candidates Walking a Tightrope Over the Fight on Terrorism.” Havana Files Julie Hirschfeld Davis sends a quick report from Havana on President Obama’s remarks on the attacks; Hanna Ingber, an editor in New York, adds it to the blog. Twitter Updates Rukmini Callimachi, The Times’s terrorism specialist (who is at home in her pajamas, on what was a planned day off), begins tweeting a series of facts, observations and insights.

The series is later compiled by Michael Luo, the deputy metro editor, into a single collection. ‘Islamic State has claimed responsibility’ Ms. Callimachi reports ISIS’ claim of responsibility. The news is posted to Twitter three minutes later. Home Page: Redesigned After consulting with Mr. Levy and other digital editors, Amy Padnani, a senior home page producer, redesigns the home page to prominently feature the attacks. For Print: An Accelerated Production Schedule Alan Robertazzi, editor of news production, emails the newsroom an update on the print schedule: “Because of the heavy volume of news on the Belgium terror attack, we will have EARLY DEADLINES FOR FIRST NATIONAL EDITION on all non-terror pages.” Suspect Photos Craig Allen, a picture editor, publishes photos of the suspects. Within minutes, the photos — confirmed by the Belgian federal prosecutor’s office — are posted on The Times’s live blog and Twitter feed. Wanted: Extra Copy Editor Ms. Rudoren requests an additional copy editor and suggests that the sports copy desk help relieve the overburdened international desk by editing the coverage of a baseball game in Cuba. Reporters Arrive in Brussels Mr. Bilefsky and Ms. de Freytas-Tamura arrive in Brussels eight hours after leaving London. (The Eurostar trains to Brussels were not running; the two reporters took a train to Paris and then drove from there to Brussels.) Explosions at Airport Two bombs explode at 7:58 a.m. local time in the departure hall at Brussels Airport in Zaventem, Belgium. Explosion at Subway A bomb explodes at the Maelbeek subway station.