I'm sure I've read that pigs actually can't raise their heads enough to see the sky - it's a famous piece of animal trivia, like bats turning left out of their caves. I couldn't swear to it - over to you QM.
even if thats true, pigs can definately roll on their sides and backs meaning that they can then look skyward! but i do understand that their eyesight isn't that great so they probably don't go in for much cloud glazing or plane spotting.