Using these missiles to down civilian aircraft is simply immoral and totally unjustifiable.用这些导弹击落民用飞机是极不道德也是完全没道理的。Shortly after the take-off, the civilian plane was skyjacked by three armed men.起飞后不久，这架民用飞机就被三个带武器的男人空中劫持了。Civil aircraft engines must be quiet, non-polluting, reliable and long-lasting.民用飞机的发动机必须噪音低、无污染、可靠、耐用。