NEW YORK, NY (AP).- Flight attendant Betty Ong couldn't tell exactly what was happening in the cockpit of American Airlines Flight 11, but it was clear to her that there was trouble.

"I don't know, but I think we're getting hijacked," she said in a phone call to an American Airlines reservation desk at 8:19 a.m. on Sept. 11, 2001.

The audio recording of that call — her relaying that two other employees had been stabbed, that they couldn't get into the cockpit and didn't know who was in there, that someone had sprayed something into the air, the long stretches of silence on the other end of the phone as her listeners seemingly struggled to fully absorb what they were being told — is part of an online timeline that attempts to give a sense of order to that most chaotic of days.

The timeline, put together by the National September 11 Memorial & Museum and launched Wednesday, incorporates audio recordings from phone calls on that day, oral histories from survivors and eyewitnesses and graphic photographs and video snippets arranged in chronological order. Viewers can use social media including Facebook and Twitter as well as e-mail to share links to the site and to particular photos and videos.

The timeline starts at 5:45 a.m., with photographs of hijackers Mohammed Atta and Abdulaziz al-Omari passing through airport security in Maine for a flight to Boston, where they would board Flight 11. It ends at 8:30 p.m., with President George W. Bush addressing the nation.

Along the way, it outlines the departures of all four fatal flights and shows images of their passenger manifests, video and photos of the World Trade Center's north and south towers after they were hit and heart-breaking moments such as when United Airlines Flight 175 passenger Brian Sweeney left a voicemail for his wife, Julie Sweeney.

"Jules, it's Brian. Listen, I'm on an airplane that's been hijacked. If things don't go well, it's not looking good, I just want you to know I absolutely love you," he said.

The timeline doesn't shy away from the starkest images of the day. In one video of the collapse of the south tower, an onlooker can be heard saying, "Oh, my God!" repeatedly as the tower falls. A video of the fall of the north tower carries a warning of mature language, as people can be heard screaming and cursing, including a man saying, "That's a (expletive) bomb!"

The president of the museum, Joe Daniels, said the project's organizers were sensitive to the nature of what they were presenting and took steps such as leaving it up to viewers as to whether they wanted to take closer looks at specific photographs and videos or listen to particular bits of audio.

"We are the institution that needs to preserve the history of what happened," he said. "That means taking on some of the difficult material. That means reminding people of some of the difficult stuff."

Charles G. Wolf, who lost his wife, Katherine Wolf, at the World Trade Center, said it was a good thing that the museum was putting this material out there.

"We don't want it to be sugarcoated," he said. "We want people to understand what it was like."

The images may be difficult for some Sept. 11 family members and others to look at, but they can choose not to, Wolf said. He contrasted that to what he expects the atmosphere will be like closer to the 10th anniversary in September, when it's likely images from the event will be more prevalent on television and elsewhere and will be more difficult for people disturbed by them to avoid.

"Unless you choose not to turn the television on, you're going to be hit by this stuff later this year," he said.

The destruction at the Pentagon, the evacuation of lower Manhattan and the few extrications of people trapped in the debris are all in the timeline, as are images of items including the dusty and dirty shoes that were worn by people as they left the stricken towers and political candidates' notices for the primary election New York City was expecting to hold that day.

Compiled from the museum's collection, the timeline is an effort to help people get a sense of how that life-altering day unfolded, Daniels said.

"It takes an incredibly chaotic day that changed the world and organizes it in a way that is accessible to large numbers of people," he said, pointing out, "No matter where you were, it was confusing."

The timeline's use of social media allows viewers to share it in a personal way, said Mike Lucaccini and Danny Riddell, founders of Archetype International, the San Francisco-area company that designed and developed it. If there's a particular moment of the day that someone wants to share, he or she can do that.

"It's such a personal experience for everyone," Lucaccini said. "A specific moment in time may mean something to someone in particular."

Alice Hoagland, who lost her son Mark Bingham on United Airlines Flight 93, is thrilled to be part of the timeline. It includes a voicemail message she left for her son, telling him that terrorists would probably be trying to use the plane to hit a site on the ground and to do what he could to prevent it.

"I would say go ahead and do everything you can to overpower them because they're hell-bent," she said in the message.

Reached Tuesday in Los Gatos, Calif., Hoagland told The Associated Press that she hadn't seen the timeline yet but that "it's a tremendously good teaching tool for people who want to understand the events of that day."

While the general content of the timeline is similar to material about Sept. 11 that has been seen before, the project organizers focused on trying to use specific items that haven't been in the public eye previously, said Jan Ramirez, chief curator at the museum.

"What we wanted to do was try to avoid the more iconic . material that has been out on the Web and in films," she said, in favor of "evidence that was documented by the everyday people who were entangled in this event."

Copyright 2011 The Associated Press.