下面三句所表达的意思不同:
His grandma never travelled by air in her lifetime.
他祖母一辈子都没坐过飞机旅行。
(表示一辈子没乘过)
His grandma has never travelled by air in her lifetime.
至今他祖母还没有坐过飞机旅行。
(从出生到现在不曾坐过)
His grandma said she had never travelled by air in her lifetime.
他祖母说她从没坐过飞机旅行。
(从出生到说话时还未坐过)