"We mourn those who perished as they performed their work, whether in rescue efforts, in offices or on airplanes," said AFL-CIO President John Sweeney. "Already, union members have gone into action to assist the rescue efforts, and the AFL-CIO and our unions will do everything we can to assist the continued rescue operations and the medical care of those injured."
Among the deaths resulting from the airliner crashes into New York's World Trade Center buildings and the Pentagon outside Washington, D.C., were unprecedented losses of union emergency services workers.
The fate of hundreds of other union workers remains unknown.
Members of the International Association of Fire Fighters (IAFF) are among the hundreds of rescue personnel still missing or presumed dead.
IAFF General President Harold Schaitberger said the World Trade Center catastrophe "will undoubtedly be the worst day for line-of-duty deaths in the 83-year history of the IAFF."
The four hijacked airliners used in Tuesday's attacks carried a total of 233 passengers, 25 flight attendants and eight pilots.
Captain Duane Woerth, Air Line Pilots Association president, said his union has "committed all of the resources of the association's security, air safety and accident investigation personnel to assist in this unimaginable tragedy."
A Flight Attendants Association statement said the union stood "ready to assist authorities and families of victims in any and every way possible."
More than 30 electrical workers, painters, laborers and steam fitters worked on construction projects in the World Trade Center and are unaccounted for, according to New York City Building and Construction Trades Council President Edward Malloy.
In addition to the teams of union emergency services and medical workers conducting rescue and aid missions in New York and suburban Washington, D.C., union volunteers are contributing their skills, funds and even blood.
More than 1,000 Iron Workers from the mid-Atlantic and New England area have volunteered their services for rescue, recovery and cleanup in New York, according to the union's national headquarters.
The New York City Building and Construction Trade Council reports working around the clock, with about 1,000 people assisting in New York's rescue and cleanup work.
Employees of Washington-area unions and other concerned citizens are invited to join AFL-CIO headquarters staff for a brief memorial moment of silence at noon today featuring faith leaders from several religious traditions.
AFL-CIO suggests visiting www.aflcio.org for developing information and opportunities to help