Melissa Hughes left an answer phone message
Melissa Harrington Hughes was in New York attending a financial conference, staying in the Marriott Hotel on floor 101 of the World Trade Center's north tower.
"Sean, It's me. I just wanted to let you know I love you and I'm stuck in this building in New York.
"A plane hit the building or a bomb went off, we don't know, but there's lots of smoke and I just wanted you to know I love you. Bye bye."
Her husband was asleep when the message came in, and tried to return her call.
"I immediately tried to call her on her cellphone and it wouldn't go through," he said.
"It later went to voice mail and still to this point her voice mail is full, so you can no longer leave a message."
All he could do was watch in horror as the tragedy unfolded on television.
The fate of his wife is unknown.
'I know we're all going to die'
Terrified passengers on board the hijacked planes made frantic phone calls to their families before crashing.
Mark Bingham, 31, who was on Flight 93 which crashed near Pittsburgh, Pennsylvania, rang his mother minutes before the impact.
Alice Hoglan broke down as she told reporters: "He said: 'I want you to know that I love you very much and I'm calling from the plane.
"He said: 'I'm in the air. I'm calling on the air phone of the airplane. We've been taken over, there are three men that say they have a bomb.'
"And I said: 'Who are they?' And he repeated that he loves me and I think he said 'I don't know who they are'.
"He became distracted there, as if someone else was speaking to him. He said something to the effect that it was true... and then the phone went dead."
Flight attendant CeeCee Ross-Lyles, also on Flight 93, called her husband at home in Fort Myers, Florida, according to her aunt.
"She called him and let him know how much she loved him and the boys," Maria Schneider said.
As people screamed in the background, Ms Ross-Lyles sobbed: "We've been hijacked," and the phone went dead.
An unnamed passenger on the same flight locked himself in one of the plane's lavatories and called 911.
Dispatchers who answered the phone said he repeatedly said: "We are being hijacked, we are being hijacked, this is not a hoax."
"He heard some sort of explosion and saw white smoke coming from the plane and we lost contact with him," said Westmoreland dispatcher Glenn Cramer.
Thwarted by passengers
Businessman Thomas Burnett of San Ramon, California, called his wife, the family's priest told reporters.
The Reverend Frank Colacicco described how Mr Burnett said: "I know we're all going to die - there's three of us who are going to do something about it."
Then he told his wife: "I love you, honey," and the call ended.
A senior US intelligence official told MSNBC.com that mobile phone communications from Flight 93 indicated that three passengers overpowered the hijackers but were unable to maintain control of the plane.
On that plane, a pilot secretly turned on the microphone, allowing passengers to hear everything that was being said by the terrorists - a warning that may have prompted some passengers to attempt an act of heroism that presumably saved another national landmark.
Cockpit coversation overheard
CNN commentator Barbara Olson was on board the American Airlines Flight 77 which crashed into the Pentagon in Washington.
She called her husband, senior Justice Department official Theodore Olson, to tell him the plane had been hijacked.
"They had knives... they rounded up the passengers and the pilots in the back of the plane," she said.
Her last words before she was cut off were: "What do I tell the pilots to do?"
Businessman Peter Hanson, who was with his wife and baby on the United Airlines flight 175 that hit the World Trade Center, called his father in Connecticut.
Despite being cut off twice, he managed to report how men armed with knives were stabbing flight attendants, apparently in an attempt to force crew to unlock the doors to the cockpit.
"A stewardess has been stabbed... the plane is going down," he said, before being cut off.