Mr Martin Coughlan (53) was working on the 97th floor of the World Trade Centre when terrorists attacked.
The carpenter from Cappawhite, Co Tipperary, a married man with four daughters, had been living in the Queens district of New York for 14 years.
In Tipperary, his sister-in-law, Ms Bridget Coughlan, spoke for many Irish people when she expressed shock that the tragedy had touched her family.
"You never think something like this would hit you, your family, your home," she said. "Trying to come to terms with something like this is so hard."
Speaking from Coughlan's Bar on Main Street, Tipperary, Ms Coughlan said the family was still hoping for a miracle.
"We're hoping, praying that some miracle might happen and he'll be found, but as time goes on it's just so hard to believe it," she said.
"Things are looking very bad and we're just praying and hoping and trying to support each other."
Ms Coughlan said she was in constant contact with Mr Coughlan's wife, Catherine, in America.
"She just doesn't believe it, I suppose. It's so hard to believe somebody you love is gone," she said.
"I just don't know how she's coping really. She just has the girls around her. We can't do anything from here."
Mr Coughlan's four daughters are Orla (27), Eilis (25), Sinead (22) and Denise (17).
He has three brothers - Finbar, Paddy, who lives in Cappawhite, and Jimmy, in Dublin - and a sister, Ann, in Tipperary.
Mr Coughlan is understood to have called his wife in the immediate aftermath of the attack but has not been heard of since.
