VOA慢速英语:越南获准开通直飞美国航班

code - n. a set of letters, numbers, symbols that identifies something, like airplanes

assessment - n. the act of making a judgement about something

maintenance - n. the act of keeping property or equipment in good condition by making repairs, correcting problems, etc.

aviation - n. the business or practice of flying airplanes, helicopters, etc.