The first commercial supersonic era, from 1969 to 2003, had some well-documented issues. There was the tragic crash of Air France Flight 4590, a Concorde jet that went down in flames just after takeoff in July 2000. There was the window-rattling sonic boom produced by successful flights, which precluded airlines from scheduling overland routes. And there was the cost of fueling four gas-guzzling turbojet engines, which required 6,770 gallons of fuel an hour to reach and maintain a cruising speed of Mach 2—just under 1,500 miles per hour.
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