Can I fly from the US to Spain with a Pocket knife in my luggage? Not as a carry on obviously.?

From personal experience, the Spanish will hand search your bags if they want to. I'm talking about luggage (not carry-on) at the final destination. I had my bags completely emptied out because a bottle of perfume had broke and it leaked to the outside. They'll send the bag through an xray and then decide if they want to let you go. I imagine if they spotted any size knife, they might confiscate it. Mail it through USPS or FedEx to be safe. Or just buy one when you get there and toss before you head home. If that is one of your favorite knives, I wouldn't risk it being taken away at the airport. The Spanish aren't the fondest of us Americans, I'd be on the safe side.