If we tried before?

U.S. Military Wanted to Provoke War With Cuba

In the early 1960s, America's top military leaders reportedly drafted plans to kill innocent people and commit acts of terrorism in U.S. cities to create public support for a war against Cuba.
Code named Operation Northwoods, the plans reportedly included the possible assassination of Cuban émigrés, sinking boats of Cuban refugees on the high seas, hijacking planes, blowing up a U.S. ship, and even orchestrating violent terrorism in U.S. cities.
The documents show "the Joint Chiefs of Staff drew up and approved plans for what may be the most corrupt plan ever created by the U.S. government," writes Bamford.
The Joint Chiefs even proposed using the potential death of astronaut John Glenn during the first attempt to put an American into orbit as a false pretext for war with Cuba, the documents show.
Should the rocket explode and kill Glenn, they wrote, "the objective is to provide irrevocable proof … that the fault lies with the Communists et all Cuba [sic]."

Or even a plane flying in to a building? Sound far-fetched?

Clearly demonstrates that we should question everything. Look under every rock. Don't just take our "leaders" word for it. Look deeper. Look at all sources. Listen to those "conspiracy nuts." They may be on to something.