On September 11, 2001, Al-Qaeda terrorists used four Boeing planes as weapons, crashing them into the World Trade Center towers in New York, the Pentagon, and a fourth aircraft crashed in a field in Pennsylvania after the action of the crew and passengers. The tragedy caused the almost total paralysis of commercial air traffic in the United States, with only 252 flights the day after the attacks, when the previous day had seen 38,047 flights. The recovery was rapid but not total, and it was only after three years that the traffic levels of the year 2000 were reached and surpassed.
The attacks profoundly transformed security in aviation. Reinforced cockpit doors with electronic locks were implemented, stricter passenger controls that included shoe removal, and prohibitions on sharp objects. In the United States, the Transportation Security Administration was born and advance passenger information systems were created. Subsequent attempted attacks led to additional restrictions such as the limitation of liquids to 100 centiliters, the removal of computers from carry-on bags, and the introduction of body scanners.
From an economic point of view, the attacks triggered financial devastation in the sector. United Airlines shares fell 42% on the stock exchange reopening and American Airlines shares fell 39%. American airlines ended 2001 with losses of 8 billion dollars, in contrast to the 2.2 billion dollars in profits from the previous year, and the global industry recorded losses of 13 billion dollars. The Bush administration had to approve an aid package of 5 billion dollars and 10 billion dollars in loan guarantees, assuming the role of last resort insurer after insurers canceled terrorism policies.
The crisis led to the bankruptcy or reorganization of several airlines, including Swissair, Sabena, US Airways and United Airlines. The following decade was marked by an intense consolidation movement, with Delta absorbing Northwest, United acquiring Continental and American buying US Airways. Simultaneously, low-cost carriers gained market share, with Southwest and Ryanair growing significantly. In 2026, 5.1 billion passengers were transported, three times more than in 2000, although low profit margins continue to keep the sector vulnerable.
