By Justin Bachman, Bloomberg News Ask a harried air traveler about the basics of modern flight, and you’ll probably elicit surprise when they discover commercial airplanes fly only as fast as they did in the 1950s. Given the range of aerospace advances in the past half-century, plus the technological leaps in almost every other area of human endeavor, it seems reasonable to ask: Why can’t we fly faster? That’s the question driving a Colorado startup called Boom Technology, which says it’s time to bring supersonic jet travel into the mainstream-in a modern way.