Sit on a mat and place a medicine ball on the right side of your hips. (blog.fitplanapp.com)
This figure four stretch targets the outer sides of the hips and thighs, which can help loosen up your lower body so you'll be more comfortable sitting on an airplane. (health.com)
Twist to one side, bringing the kettlebell to the outer side of that hip; then repeat in the other direction. (pumpsandiron.com)