Melissa Doi, a 32-year-old manager at IQ Financial Systems on the 83rd floor of the World Trade Center's South Tower, spoke to the emergency services for at least four minutes.

Doi, her terror-stricken voice contrasting starkly with the purposefully emotionless tone of the operator, described how the heat is making it hard to breathe.

"I"m going to die aren't I?" she cried.

"No, no, no, no, no." the operator responded.

"I'm going to die."

"Ma'am, ma'am, say your prayers," the operator said, trying to console her.

"Please God," Doi said.

The conversation apparently ended shortly after, Doi crying in a ragged

voice: "help!"

Among the other futile calls to the emergency services was a desperate last cell phone contact from insurance broker Kevin Cosgrove, just as his 99th-floor office disintegrated in the South Tower.

"Oh my God.... Aaaaarrggggghhhh!" Cosgrove, vice president of brokerage firm Aon Corp, is heard shouting at 09:58 am, his voice fading, amid crashing sounds of the collapsing tower, before the line cuts.

Passengers and crew on the four airliners also made heart-breaking last attempts to reach out to the living.

Brave flight attendant Betty Ong, on American Flight 11 from Boston, called ground control, calmly describing how two colleagues had been stabbed and "the cockpit's not answering the phone."

"I think we're getting hijacked," she said at 08:19 am. Less than half an hour later Ong and the rest of those on the plane disappeared in a fireball in the North Tower.

Alice Hoagland, mother of United Flight 93 passenger Mark Bingham, tried to call her son after seeing the shocking news. He didn't answer, so she told him, her voice remarkably calm and mother-like: "Try to take over the aircraft....

Group some people and do the best you can to get control."

Bingham, whom she calls "sweetie" in the message, is believed to have helped lead an insurrection against the hijackers that sent the plane crashing into a Pennsylvania field, rather than its likely target of Washington, DC.

Seated on United Flight 175 just minutes before it smashed into the South Tower, Brian Sweeney also left a message, in this case to his wife Julie.

Following a chirpy, automatic "message one!" heard on the answering machine, his words are simple and moving.

"Listen, I'm on an airplane that's been hijacked," he says. "I just want you to know I absolutely love you. I want you to do good, go have a good time.

Same to my parents and everybody. I totally love you."

The majority of victims' families never had a chance to say goodbye, or, in many cases of those killed at the World Trade Center, even to identify their vaporized remains.

But a different sort of anguish afflicted those who were able to exchange final words.

Beverly Eckert remembered how happy she was to receive a call from her husband Sean Rooney at about 09:30 am: she assumed he'd been able to escape from his office in the Twin Towers.

But "he told me he was on the 105th floor, and I knew right away that Sean was never coming home."

After long minutes of talking, he whispered "'I love you' over and over.

Then I suddenly heard this loud explosion," Eckert, who died in 2009, wrote in comments published this week in New York magazine.

Her husband was still alive but they both knew what the sound was: the tower starting to collapse.

"I called his name in the phone over and over. Then I just sat there huddled on the floor holding the phone to my heart."