Just because you're 30,000ft in the air, strapped to an airplane seat doesn't mean you can't exercise. The Airplane workout is no substitute for a HIIT program or a strength-building fitness routine but considering that you're making use of downtime to keep your muscles humming, your circulation going and your brain and attention lively, then this is a workout you should make sure you take with you along with your in-cabin luggage and obligatory viewing material on your tablet.