American Airlines Flight 444 was a Boeing 727 flying from Chicago to Washington DC, which on November 15, 1979 was attacked by the Unabomber. The bomb planted in the cargo hold failed to detonate, but gave off large quantities of smoke, and twelve passengers had to be treated afterwards for smoke inhalation. It was later determined that the bomb was powerful enough to have destroyed the aircraft had it worked correctly.
This was not the first Unabomber attack, but it was the attack which led to the FBI investigation into the Unabomber, as airliner bombing is a federal crime.
American still uses the Flight Number 444 despite the incident. The number may operate several different routings over time as American routinely reassigns flight numbers that are not flagship routes to different sectors; as of November 2010, flight number 444 is used on a San Antonio-Chicago O'Hare routing, and uses a McDonnell Douglas MD-88 (McDonnell Douglas MD-80) instead of a Boeing 727.