However, IF it was a fuel tank that fell, it was from an Iranian Air Farce plane. Those can be and generally are equiped with "drop tanks" to extend the range of an aircraft. Most of ours can carry 3- 1 under each wing and 1 slung centerline.
Besides extending the range, the drop tanks have another advantage. When the aircraft takes off, they are burning fuel from the drop tanks. Then, if they get into a fight, they drop the tanks & start fighting with a "full load" of fuel.
I appreciate your explanation. That does help make things clearer to me.