不翼而飞

bù yì ér fēi

to disappear without trace

to vanish all of a sudden; to spread fast; to spread like wildfire

不

bù

no; not so

翼

yì

alternative name for 絳|绛[Jiang4], the capital of the Jin State during the Spring and Autumn Period (770–475 BC)

而

ér

and

飞

fēi

to fly