The aircraft had reached its cruising altitude of about 39,000 feet.飞机已达到约3.9万英尺的巡航高度。

I've never flown at this altitude before.我以前从未在这一高度上飞行过。

It was very hard in extreme heat and at altitude.炎热天气和高海拔环境让人非常难受。

an airliner flying at high altitude一架在高空飞行的大型客机

These altitudes are frequently wrapped in storms.这些高地常刮风暴。