Note: iCloud connection is for looking friends who also uses App in the Air and sync across iOS devices. If you want to Import flight from your iCloud email, connect it via IMAP option.
When you connect iCloud in the app's settings, you might see an error that says "...you need to enable "iCloud Drive" and check access for the app to the option "Look me up by e-mail"...". This is needed to show your friends who also uses App in the Air in the Leaderboard.
To solve this error, you need to check the settings on the device itself and a Mac computer (if you have one).
Open device settings and select your Apple ID at the top
Scroll a bit down and check that iCloud Drive is enabled
Then scroll to the bottom and open "Look me up" option.
Turn on for the App in the Air.
Mac computer settings:
Open system settings
At the top, near iCloud Drive tap on "Options"
Select "Look me up by email" bookmark
Turn on for "com.apple.cloudkit"
Save changes ("Done" button)