The list also included other plots to bomb several sites in Britain in 2004 ; to attack Heathrow Airport in London using hijacked commercial airliners in 2003 ; to attack Westerners at several places in Karachi , Pakistan , in spring 2003 ; toattack ships in the Persian Gulf in late 2002 and 2003 ; to attack ships in the Strait of Hormuz , a narrow part of the gulf where it opens into the Arabian Sea , in 2002 ; and to attack a tourist site outside the United States in 2003 .