[Orbiter]

I’ll repeat the gist of a comment I posted on FR years ago: there is no way in hell that aircraft departed for a transatlantic flight with an empty center fuel tank.

[bootless]

>> there is no way in hell that aircraft departed for a transatlantic flight with an empty center fuel tank.
<<

Agree.

[Moonman62]

For structural reasons, wing tanks are filled first, and then any remaining fuel needed for a particular flight is put into the CWT. The volume of the 747-131’s CWT, by all standards, is large. It has a Jet A fuel capacity of 86,363 pounds (12,890 gallons). Based on the length of TWA’s flight to Paris, fuel in the center wing tank was not required. As with all transport airplanes, even this “empty” tank still contains a small amount of unusable fuel, estimated at around 50 gallons, and resides in small “pockets” and trapped areas on the lower tank surface.

http://lessonslearned.faa.gov/ll_main.cfm?TabID=3&LLID=21&LLTypeID=2

[Lower Deck]

I’ll repeat the gist of a comment I posted on FR years ago: there is no way in hell that aircraft departed for a transatlantic flight with an empty center fuel tank.

Sure they would. The distance between New York and Paris is about 3600 miles. A 747-100 fully fueled can fly 6100 miles. The airplane would carry enough fuel to make the trip with a safety margin but it's not going to haul fuel it doesn't need.