I generally can sleep pretty soundly if I'm exhausted, but must admit that trying to do so in an economy class seat can be challenging. Besides the narrow seats and limited legroom, my head keeps flopping about. Those rounded neck pillows offer some relief but aren't all that comfortable.
While I've not tried it, I'm intrigued by this new nap pillow. Please go to this link to read more.
(photo courtesy of Conde Naste Traveler)