Il volo dell'Alitalia e' decollato con diciotto minuti di ritardo.
The Alitalia flight took off eighteen minutes late.
It can also be used figuratively, "to take off" in the sense of to get off the ground, become successful or established.
Il piano del governo non e' mai decollato.
The Government's plan never took off.
The opposite of decollo is atterraggio, landing (verb, atterrare). Because atterraggio obviously contains the word for earth (terra), the Italians coined a new word when man landed on the moon, allunaggio (containing the word luna, moon).