The airplane took off effortlessly.

Literal

Airplane [topic-は], effortlessly took-off.

楽々 (らくらく) is a reduplicative adverb meaning 'with ease, effortlessly,' formed by doubling 楽 ('comfortable/easy'). The と marks it as an adverb modifying the verb. This kind of ABAB-pattern reduplication functions like a 擬態語 in Japanese.