iOS 17.4 added a new permission request for apps that need to access the internal barometer.
AvTraffic needs this to determine your current pressure altitude and your altitude by applying the nearby QNH.
Apple has included this permission with the 'Motion and Fitness Sensors' section of the 'Privacy and Security' iOS Settings.
If you get asked to give AvTraffic permission to access the 'Motion and Fitness Sensors', please reply yes.
Understandably, you may wonder why AvTraffic needs to access the 'Motion and Fitness' sensors. But it is only the barometer that is being accessed.