。
I like watching planes take off.
Literal
I [topic-は] plane [subject-が] take-off-[go-away-ていく] [nominalizer-の]-[object-を] see [nominalizer-の]-[subject-が] like [is-だ].
A nested nominalization: the embedded clause 飛行機が離陸していく ('planes take off and fly away') is nominalized with の and made the object of 見る. Then the whole perception clause 飛行機が離陸していくのを見る ('watching planes take off') is nominalized again with の and becomes the subject (with が) of 好きだ. Double の-nominalization is typical for 'like doing X' sentences with complex objects.