I knew little about your arrival until your mother told me o

翻译：在飞机上你母亲跟我说起之前,我几乎不知道你来了.
这句话中little 表示“几乎不”,本身就是一个否定词,所以不用not,楼主想要用not的话可以改为：
I did not know about your arrival until your mother told me on the plane
楼主要注意几个常用的表示否定的词如：little,few ,hardly,never 等,
比如:I never get a guitar until he gives me one （这句话中 never get 楼主就可以理解为 don't get）