Concorde flights came to a screeching halt after only 27 years of operation on October 24, 2003. The reason? Excessive cost, high fares, and loud noise. On a regular flight, Concordes consumed 6,771 gallons of fuel, which quickly exceeded the profit made from the flight. In addition to that, only a total of 20 Concordes were built and no airline ordered them except for Air France and British Airways, who had to as they were state-run airlines at the time.
Oh, and a 2000 crash that killed everyone on board (109 people) and four people on the ground.
modern day terrorists can't be bothered with such extravagant, risky and expensive methods as hijacking a plane, they prefer less complicated and cheaper ones like driving into a crowd of people or a mass shooting