Sleep tracking using Pillow on the Apple watch with Airplane mode enabled is not going to be affected. However, depending on the mode you have selected, you have to be careful when you enable Airplane mode:
​
​Sleep Cycles only mode
If you use Pillow on the Apple Watch in “Sleep cycles” mode (no audio recordings and no alarm), you can enable Airplane mode anytime and start your session on the Apple Watch. When you wake up, remember to enable Airplane mode before you press “Stop” in Pillow. This will ensure the Apple Watch has enough time to re-establish the connection to the iPhone and synchronize your sleep analysis data. If you enable Airplane mode after pressing "Stop" and the analysis completes, simply make sure your data is synchronized and if it hasn't, 3D touch anywhere on the screen to synchronize your data manually.
​
​All other modes
If you have selected to record a session using Pillow on the Apple Watch with audio recordings and/or Alarm it is important that you enable Airplane mode after you start the sleep session. When you wake up or the alarm sounds, it is highly recommended that you disable Airplane mode before stopping your sleep session in Pillow to ensure a connection between your devices has been established. Also please note that Snoozing the alarm from the Apple Watch is not possible while either of your devices is in Airplane mode. If you enable Airplane mode after pressing "Stop" and the analysis completes, simply make sure your data is synchronized and if it hasn't, 3D touch anywhere on the screen to synchronize your data manually.