The 9/11 Commission Report states that:
“The 19 men were aboard four transcontinental flights. They were planning to hijack these planes and turn them into large guided missiles, loaded with up to 11,400 gallons of jet fuel. By 8:00 am on the morning of Tuesday September 11, 2001, they had defeated all the security layers that America’s civil aviation security system then had in place to prevent a hijacking.”
The attackers actually selected crosscountry Boeing 767 aircrafts because they were full of fuel. They didn’t select Airbus aircrafts because they had an autopilot feature that didn’t allow them to crash into the ground.