Thanks for contacting the World Warfare support team.
We have been made aware of a bug with the display time of fuel not syncing in real-time; there is a countdown timer for your aircraft indicating when you may be running low on fuel that I believe as for now you have to keep refreshing. For the longest time that has been an ongoing issue in which we have investigated and with this latest update put in a 30-minute low-fuel warning notification to inform you of your aircraft running low on fuel.
We do apologize for the inconvenience and still suggest you send them home earlier than what the timer indicates just to be safe.
We have been taking feedback about this regarding putting a notification in-place so that you are informed beforehand when you are low on fuel. You can check the link out here to see what's being discussed:  http://www.worldwarfare.com/topic/1344-new-notification/
You can also visit this link to see what players had been discussing about this topic and for any comments or updates made by our moderators prior to this latest update: