Trends in air travel : The major incident in recent years to impact longer distance travel was the series of terrorist attacks on the US in September 2001. The effect was chiefly in the US and mostly on air travel. International travel of all kinds and non-business travel declined the most after September 2001. Business travel was relatively unchanged. The number of shorter long distance trips. These trips are almost all made by car. The impact of the events of September 2001 in the US is evident in the data on domestic and international travel throughout the world. By 2005 air travel had returned to the trend of mid-and late1990s.