The speed of an airplane is far greater than that of a helicopter.
Literal
Airplane [possessive-の] speed [topic-は] helicopter [possessive-の] that [comparative-より] far-more fast.
それ serves as a pronoun replacing 速度 to avoid repetition — 'that (= speed) of a helicopter.' はるかに means 'by far, much.' This uses the standard comparative pattern AはBより~ ('A is more ~ than B').