This flag will allow players who are allowed access to the field to fly within it. This is handled via a timer, so leaving the field, teleporting away etc. will not allow the flying to be abused.
If the player is not within the a field with the flag, they will have a number of seconds to land before their flying ability is removed. They will be warned once a second until that time has expired. The default is 3 seconds, but can be changed in the config with the fly_warn_seconds option.
As always, if you have any questions, comments or concerns, please let me know!