Why divert to LAX instead of going back to SFO? Is it just a scheduling thing, e.g., it would take longer to get a replacement plane to continue the flight from SFO than it would to fly to LAX and get a replacement there?
A plane heading to Japan from SFO would be carrying quite a bit of fuel. It's possible / likely that the takeoff weight would exceed the safe landing weight, requiring circling to burn off fuel or dumping fuel. If they have to get rid of fuel anyway, it might make sense to continue to another airport where they could get a replacement aircraft.
In addition to that, SFO is already down a runway which is causing some delays because planes need to go around the construction zones. An airplane with a potentially damaged landing gear can close all of the remaining runways due to the cross layout that SFO uses. LAX is laid out a little differently, so you aren't risking having the whole airport close for a while if something does go wrong.
When combined with the need to burn off some of the fuel, LAX seems like a sensible choice. You don't need to travel over any particularly tall terrain, LAX is large and should have sufficient runways for an airplane that might have trouble coming to a stop quickly. Since there was no issue with actual in-flight operation of the airplane, it's also not a 'land right the frak now' situation.
Is SFO a maintenance hub? That could be another variable, if the repair facilities in LAX are better.
And then there’s a potential bias against SFO, given they just let an airplane take off that HAD A WHEEL FALL OFF. Maybe they aren’t the best party to examine the plane just now.
There's probably 1000 major aviation incidents each year, every year, for many decades. We're submitting Hacker News articles on every one now? Why? We never did before.
"Major" is sufficient to remove an aircraft from service.
Globally:
According to ACRO, recent years have been considerably safer for aviation, with fewer than 170 incidents every year between 2009 and 2017, compared to as many as 226 as recently as 1998. {1}
Tires falling off of a passenger plane isn't "major", nor is it common - it's a rare occcurence, one that should never happen, and something that has the potential to cost lives.
Why are reports being submitted now?
It's only recently become common knowledge that various aircraft companies that were once the pinnacle of safety practices (eg: Boeing) are now relatively rotten to the core and troubled with cost cutting practices and a lack of safety culture.
This was a 777; those planes aren't in production any more, so this plane is probably at least 10 years old I'm guessing. This isn't a factory or design issue, this is a maintenance issue, and that falls on the airline, United.
Well, at least it wasn’t the front that fell off.