An American Airlines jet carrying 58 passengers crashed into the Pentagon yesterday mornin less than an hour after two planes crashed into the World Trade Center, an apparent wave of terrorist attacks that triggered chaos in Washington and New York and dismay across the nation.

The aircraft, Flight 77 from Dulles to Los Angeles, was a Boeing 757 that eyewitnesses said flew low and fast in a direct hit on the west side of the five-sided building. Glenn Flood, a Pentagon spokesman, said there were "extensive casualties" and an unknown number of fatalities, according to Associated Press. "We don't know the extent of the injuries," he said. A spokesman for Giant Food Inc. said the grocery chain had been asked by Pentagon officials to supply a refrigerated truck to carry bodies from the building.

Local hospitals reported treating dozens, many who suffered burns. Rep. Ike Skelton (D-Mo.), who had been briefed by Pentagon officials, said the attack had left roughly 100 "casualities," although it was not clear if those included wounded as well as dead.

The building that houses 24,000 workers and operates as the nation's military command center suffered heavy damage, with at least a portion of the structure collapsing, witnesses said. Shortly after the crash, witnesses reported secondary explosions and plumes of smoke that could be seen miles away.

"I was right underneath the plane," said Kirk Milburn, a construction supervisor for Atlantis Co., who was on the Arlington National Cemetery exit of Interstate 395 when he said he saw the plane heading for the Pentagon. "I heard a plane. I saw it. I saw debris flying. I guess it was hitting light poles," said Milburn. "It was like a WHOOOSH whoosh, then there was fire and smoke, then I heard a second explosion.