Erratum
Rounds 15 and 16 of the propeller section should read:
Round 15: K1, k2tog, k2, ssk, k1 twice. 12 sts.
Round 16: K1, k2tog, ssk, k1 twice. 8 sts.

From the website:

Need the ultimate accessory for the father-son dance? How about matching propeller beanies?
This wee little cap is made of washable cotton and reinforced with a hidden band of elastic to keep it on playful heads young and old, no matter how hard they flap their propellers.