[Those hollows are just as speedy as a youngster on an air scooter, and twice as determined once they've been sent out on the attack. Plus, those ghosts aren't hindered by solid objects at all - passing right through them without a care - whereas Aang may have to zig and zag. It doesn't take those ghosts very long at all to finally corner him - and when they do...well, Aang can kiss his good spirits goodbye for the next minute or so.]
I DIDN'T EXPECT ONE LIKE THAT.
Hmph, serves you right.