This is a list of some of the known false alarms on 9/11. By no means is this a comprehensive list of all false alarms of the day, but this list gives an impression of the complexity of the day.
08:45 am - afternoon: Phony bomb threats confused air traffic controllers. Reports of multiple threats were apparently the result of confusion during the early hours of the investigation and miscommunication in the Federal Aviation Administration.
08:50-10:30 am: Rumours of United Nations building hit with another plane.
08:54 am: AA77 vanishes from Indianapolis ARTCC's radar screen. They incorrectly think the aircraft has crashed, and search and rescue operations commence.
09:00-09:30 am: Martha's Vineyard Airport Control Tower evacuated due to a large white unidentified aircraft flying at appx. 2,000 ft.
09:21 am: Boston Center informs NEADS that AA11 has turned for Washington DC. In truth AA11 has hit WTC 1.
09:30 am: Reports of a third plane approaching New York. The Command Center of New York’s Office of Emergency Management based in WTC Building 7 evacuated.
09:40-09:50 am: Nashua, N.H. center (Boston Center) evacuated. A call from the New England Region informed the Boston Center about an unidentified B757 aircraft southeast of Nantucket, determined to be aimed at Boston ARTCC, and that the danger was imminent.
09:30-10:00 am: A panel truck is stopped near the NY temporary command post, with a painting of a plane and a New York skyline on it. Fearing that it might be a truck bomb, the New York Police Department immediately evacuates the surrounding area and calls out the bomb squad. The vehicle was found to be an innocent delivery truck.
09:30-10:00 am: Flight 1989 is mistakenly thought to be hijacked and to have a bomb aboard. Cleveland Center receives a total of 4 bomb threats called in concerning planes.
09:37-10:00 am: Reports of a helicopter or a small aircraft hitting the Pentagon, also LG Gas explosion mentioned.
09:43 am: A credible threat against Air Force One. The threat was passed to presidential pilot Col. Mark Tillman. Tillman asked for an armed guard at his cockpit door while Secret Service agents double-checked the identity of everyone on board. The crew reviewed the emergency evacuation plan.
09:54-10:07 am: NORAD Canada Region notifies NEADS of a possible hijack crossing the border south into Washington.
10:00 am: Reports of a suspect aircraft heading towards Johnstown, Pennsylvania airport, possibly with a bomb onboard. The control tower at the Johnstown, Pennsylvania airport evacuated. Emergency crews and firefighters being sent to the airport. Police dispatched to shut down roads.
10:00-11:00 am: Reports of a fire at Capitol Mall, explosion at USA Today headquarters.
10:00 am: Reports of fire at the State Department.
10:07 am: Baltimore ARTCC notifies NEADS of an unidentified aircraft flying over the White House. It will turn out to be the two NEADS F-16s from Langley AFB.
10:12 am: CNN reports an explosion on Capitol Hill.
10:15 am: SEADS (South East Air Defense Sector) notifies NEADS of a potential hijack entering their airspace.
10:18 am: Reports of a second plane approaching The Pentagon. Evacuation started.
10:20 am: Reports that the fire at the State Department was caused by a car bomb.
10:55 am: A warning from air traffic control to Air Force One – a suspect airliner dead ahead. Turns out to be a local farmer who had taken off from a field nearby and wasn't aware of the national ground stop.
11:00 am: A bomb is reported aboard a United Airlines jet that just landed in Rockford, Ill. Another jet disappears from radar and is thought to have crashed in Kentucky. The White House is notified that there has been another crash.
Sometime that day:
- 11 aircraft suspected hijacked.
- Rumor of a fire at the White House.
- Rumors that NYU Hospital, White House, Washington Monument, Washington Mall, and Sears Tower were hit.
- Thoughts of an explosion at the WTC, then at the South Street Seaport.
- Rumors of bombs on all the WTC buildings.
- FDNY reports of possible poison gas, not natural.
- Multiple rumors of a missile fired at WTC.
- Bomb scare at World Financial Center.
- Reports of secondary device at Stuyvesant High School.
- Bomb scare at the Empire State Building.