gcmap.com

Put in IAH-SYD or IAH-AKL. At the bottom are different controls. Select 180 minute ETOPS and 777 aircraft. Both of these routes go right through a "no-go" area in the central pacific. There are also 180 no go areas in the south Atlantic and Indian Ocean. There are polar routes that are also no go if 1 or 2 airports are not suitable.

Hence Boeing and Airbus spending millions for 330 minute ETOPS on some aircraft. There is a market for them.

Just curious, what routes are those? I've never heard of that and that far north numerous airports can be used.

Not sure. I did some very far north routes on the 777 back 13 years, but never polar routes. I just remember hearing that some of the routes had only a few alternates and if one went down you had to fly a different route. There are several airports up north of 60 deg. But if one goes down, the next suitable airport might be 70 E or W of that longitude. It might not be apparent to line pilots, as dispatch might give you different routing. I can't swear to this one.

The ETOPS no go areas in oceanic regions I do know about. They never affected UAL until IAH-AKL or SYD. LAX and SFO flights fly north of this area on a pure great circle route. Obviously different wind components could put the best route through this area.

180 mins on a polar route has multiple airports that can be used, regardless of routing.