I bet you can get the 737 across the country with only one tank of fuel. Just make sure you pay attention to the fuel flow guage and find the minimum flow number by adjusting the throttles, and don't fly full speed. My guess would be at 255 kias you'll have no problem at 33,000 feet. I've taken the FS2004 747-400 across the atlantic several times, using no where near the full fuel. I've never tried the 737, but it sounds like it may be time to do it! 🙂
I don't remember if FS2002 had a 747, but if it does, that'd be the plane to do it in.