This is the 6274th most frequent Russian word.
улетают
"Улетают" means "fly away" in English.
Here, the word 'улетают' describes a habitual action of birds flying away to the south seasonally.
Птицы улетают на юг каждую осень.
The birds fly south every autumn.
In this case, 'улетают' depicts the action of balloons being carried away into the sky.
Воздушные шары улетают высоко в небо.
The balloons fly high into the sky.
Here, 'улетают' is used metaphorically to indicate the mental transition or drift towards childhood memories.