Study of intercontinental transport of air pollutants by means of coordinated flights over the East coast of North America, the Azores and the West coast of Europe. ITOP was a component of the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT), an international initiative which coordinates the efforts of various American and European groups who have developed plans for field campaigns in the summer of 2004, with the aim of improving our understanding of the factors determining air quality over the two continents and over remote regions of the North Atlantic. The British contribution to ITOP, referred to as ITOP-UK, was funded by the Natural Environment Research Council (NERC) through the Upper Troposphere Lower Stratosphere (UTLS)-Ozone Directed Research Programme.

The ITOP-UK dataset includes trajectories and other forecast products calculated by John Methven (University of Reading), based on European Centre for Medium-Range Weather Forecasts (ECMWF) forecast wind fields, to support ICARTT flight planning, near-real-time chemical analyses produced by the University of Cambridge, and data collected aboard the FAAM Bae-146 aircraft in July and August 2004.