Can I/Should I take a Boppy pillow on an airplane? Flying alone with a four month old, help.?

I’m traveling alone with my daughter in two weeks, she will be four months old then. The boppy pillow works great at home to help hold her up and not tire out my arms, we will be on the plane for a total of 5 hours, I’m wondering if I should bring it with to help hold her since I’m traveling alone with her in my lap. Has anyone used one on an airplane? Does it fit? Do the airlines allow them? Or any other suggestions on how to make our flight easier.