In 2007, we started the Harvard Flight Attendant Health Study to better understand the health impacts of flight. Now, with thousands of participants enrolled in this study, we have created an app for the Apple Watch to study the bodys responses during an actual flight. This app is open to any interested flight attendant, pilot, or passenger. Once you enroll in our app you will answer basic questions about your personal profile, including health and work history. To allow the app to monitor the effects of flight, you will start tracking your flight through the "Start Journey" icon within two hours of your scheduled departure time and complete periodic brief symptom surveys and interactive tasks. This study also gathers biometric data from participants using wearable devices. It is recommended that you use an Apple Watch, Spire, ResMed S+ Sleep Monitor and iHealth Air Pulse Oximeter to maximize the amount and quality of data collected. These devices are not required to participate in the study, which also includes surveys and tasks related to health symptoms, sleep quality, and cognition.