Flew a lot of BCN trips (EWR-BCN) over the summer in 2008 for 4 straight months.
During that summer, one month I had 4 BCN trips on my line. We diverted on 3 out of 4 of them doing the BCN-EWR leg. Two of the stops were into Gander, and the third was into Stewart about 20 miles North of EWR. Over that summer, it was a very common problem using the B757 on the BCN run.
Some of the CA's who flew that trip a lot would have the Fuel Truck out there pumping every last drop on while having the X-Feeds open to squeeze as much as they could into the tanks.....the long taxi out did not help the gas situation either.
One problem I saw many times was when we would go BCN-EWR, we were filed on a random route. Santa Maria would often keep us 2000-3000 feet
below our "filed" altitude till reaching 30W, or sometimes 40W....this obviously threw the flt plan out the window on already an 'optimistic flt plan'. There were some guys that would declare 'min fuel' when checking in with BOS center, became somewhat common at times.
With all the deverts that I was on out of BCN (or sometimes TXL-Berlin) on the B757, when things looked we needed to stop, we coordinated around 30-40W with dispatch, and when we swung into Gander, they were great on turning us quick....down to a science. Did it once in the dead of winter for gas and de-ice and they spun us in 33 mins on to off.
I think Boeing has stretch this aircraft about as far as it's going to go, even with winglets.
Good luck and consider the stop "a little pay raise"!!
SC