To troubleshoot the issues you are experiencing with the Wizz Air app on your iPhone 13 Pro running iOS 18.1.1, please follow these steps:

1. Update the App
Ensure that you have the latest version of the Wizz Air app. Open the App Store, go to the Updates section, and check if there’s an update available for the Wizz Air app. If there's an update, install it.

2. Force Quit the App
Swipe up from the bottom of the screen to open the app switcher, then find the Wizz Air app and swipe it up to close it. Reopen the app afterward.

3. Restart Your iPhone
Restarting your device can resolve many minor issues:
- Press and hold the side button and volume button until the power off slider appears.
- Slide to power off, then after the device turns off, press and hold the side button again to turn it back on.

4. Clear App Cache
Unfortunately, iOS doesn't provide a direct method to clear app cache like Android. However, you can try uninstalling and reinstalling the app, which will clear any cached data:
- To do this, press and hold the Wizz Air app icon until it wiggles, then tap the 'X' to delete it. Go to the App Store, search for Wizz Air, and reinstall it.

5. Reset Network Settings
Depending on your internet connection, resetting network settings might help:
- Go to Settings > General > Reset > Reset Network Settings. Note that this will erase saved Wi-Fi passwords.

6. Check for System Issues
Sometimes, issues arise from the iOS version. If you notice other apps malfunctioning as well:
- It may help to perform a system update or check the Apple Community for similar issues that could provide guidance - learn more.

7. Contact Wizz Air Support
If the issue persists after trying the above, consider reaching out to Wizz Air customer support for assistance. They may have specific insights related to the app and iOS compatibility.

8. Community Feedback
To stay updated with any common problems or solutions provided by other users, you can check forums such as Reddit, or other tech discussion boards where issues related to Wizz Air app functionality are discussed - learn more - learn more.

Following these steps should help you diagnose and possibly resolve the problem with the Wizz Air app on your iPhone.

Are there compatibility issues with iOS 18.1.1 and Wizz Air app?

Sorry, I don't have enough information to answer that question accurately. Could you please ask something related to Wizz Air?