This question is for my SIL who will be traveling this weekend. Long story, but she is driving to get her almost 4 year old twins this weekend and is flying back without them. So she'll be driving with their 2 car seats (Graco Nautilus's) and will be flying back with the car seats but no kids. So what would be the best way for her to do this? Check them or gate check? Will they allow you to gate check car seats if you do not have kids with you? I would be very surprised if she still has the original boxes. She is flying Southwest if that matters.