What is the maximum range of the 738? I thought it was around 3,000 NM, yet, when I program something for a 1,890 nm flight I get an insufficient fuel warning, what am I doing wrong? Also, I can't get the LNAV button to work. Patrick Boynton

You get an insufficient fuel warning when the FMC predicts you'll have less than 2,000 pounds of fuel remaining at destination. What weight, route, and fuel amount are you using? As for the LNAV button, we need more info. When can't you get it to work.

There is a sometimes bug with the VNAV button , but the LNAV button should work if you have programmed the FMC correctly. Henri

If it was me, I would fuel the NGX up to maximum and see what happens when you re-enter the route in the FMC.

Well I was programing a flight with .1 fuel remaining, I'm not sure if it was a real route but it is LOWS to GCLP. Would I still be able to do the flight even if there is an insufficient fuel warning? How would I avoid it on something the 738 should be able to do? Patrick Boynton

How much fuel are you loading to end up with .1 after 1900nm? I know I've done a flight over 1900nm, so you shouldn't have any issues there.

Try setting reserves under 2 and around 14-18 for cost index.

What payload settings are you using? I'm not sure if you'd be able to do it with a full load of passengers and cargo?

Can you post the flight plan here? And what's your ZFW?