At the time, the best Boeing engineers were busy working on the first American  supersonic transport (SST), the Boeing 2707.

当时，最优秀的波音工程师正忙于研制美国第一架超音速运输机 (SST)，即波音 2707。

For terrestrial transportation, I don't see any real need for much advance beyond the currently planned supersonic transports, operating at almost 200 miles per hour.

对于地面运输，我认为除了目前计划的超音速运输之外没有任何真正的进步需求， 以每小时近 200 英里的速度运行。