We have to remember that the 9/11 attacks were just one of three big operations planned by al -Qaeda network.
One failed attempt was planned for Europe around the millennium festivities and intended to kill a huge number of people, while the second plan was to be executed in the USA but was foiled when an immigration officer suspected the travel documents of an Algerian coming in to the United States by way of west Canada.
http://www.arabnews.com/...
There are some definite plans for operations bigger than 9/11 but, there is no concrete proof that al -Qaeda has implemented steps for the execution of such an operation, the most daring of which is a possible attack on a nuclear power plant.
It is a fascinating article, with even more fascinating comments. Very much worth a read.