They likely will succeed in making another spectacle, but just ponder that, even on September 11, how many airliners didn't crash, how many buildings didn't come down (the Pentagon was only damaged and still stands today), and, whenever they plan or attempt another attack, they leave themselves vulnerable to arrest, maiming (no paradaisical glory there) or death (Surprise!! No virgins!!), and risk having their organization(s) revealed, detected, and compromised every time they try to pull off another mass-murder event.
Airliners crash, buildings explode, trains are derailed, school buses fail to outrun trains, and innocents are murdered every day without help from the terrorists.
As I tried to state on a local (DC) radio talk show (before I was cut off) during the "sniper" days, a sane person and populace can remain sane and functional if and only if they put things into perspective re: the incidence of death from "un-natural causes" of all kinds.
Indeed, during the "sniper crisis," only thirteen persons were killed by Malvo and Mohamad over a period of three weeks, and the dynamic duo operated over an area that was home to nearly five million trembling people.
Thus, the chances of being "sniped" during that time of "terror" was 5,000,000 people/13 victims/21 days. This works out to a probability of about 1 in 18,315 of a person being nailed by the "snipers" on a given day during their "reign of terror."
A person in their area of operation was far more likely to die as a result of a traffic accident, a fire, a fall down the stairs, the actions of an angry relative or lover, botched medical care, a pit bull attack, a drive-by shooting (especially in DC), and many other causes that are with us 24/7/365 . Not that scary, eh? And consider the thousandsa that are killed in earthquakes somewhere every few months. What I do find unsettling is the erosion of physical and mental courage on the part of so many of my countrymen, as evidenced by our obsession with terrorism, death, and whether we again will allow four groups of virtually unarmed mongrels to crash four airliners while outnumber at a level of at least 25-to-1.
"If ye are prepared ye shall not fear"...............
Off by a factor of 441. The chance over the three weeks was 13/5,000,000 = 1 in 384615. The chance for one day is that divided by 21 = 1 in 8,076,923.