I suspect that we are not meant to know how accurate the guages are. The 737-800 used to have a figure of 2.5% but it was removed. A Google search on the subject brought up an older pprune thread specifically related to the 737. Not sure about the airbus figures.

The manuals could provide a figure if they wanted to.

I kept a healthy suspicion of any fuel guage of any machine I used.

Always took an extra tonne to PMI on a Saturday morning knowing full it would be controlled chaos when they swapped runways as the sea breeze kicked in !

Well, perhaps senility has struck earlier than expected, and no, I don't recall "committing".
Neither do I recall that in a situation in which adverse weather prevents a landing you are permitted to hang around below diversion fuel in the hope that the weather will clear before you run out of fuel as seems to have happened here. What the fcuk would you do if it didn't clear? Land willy-nilly into the face of a massive Cb, windshear, lighning etc on a contaminated runway? Seriously?
What's the number of runways got to do with it? If there's a Cb dumping its contents over the field it makes no diffference if there are ten runways, they're no more use to you than one.
In my experience (and universal industry practice) if weather precludes a landing/approach as you reach min diversion fuel then you MUST divert. End of.

If I'm mistaken then please be kind enough to explain how and why I'm wrong.

because there's more than one reason for a delay than weather?

Were you there? There would have been a it of a back log of traffic for ATC to deal with and maybe they actually did have an EAT because of it.

Do you genuinely believe that any professional crew would just hang around in the hope the weather will clear? :rolleyes:

I don't have METAR/TAFs for the destination and other airports close by, but based on the METARs for PMI and that possibly a local weather pattern known as DANA, Depresión Aislada en Niveles Alto, was affecting the weather in the whole area, so it sounds like bad weather would have been forecast. Haven't flown in that area for a few decades, but used to fly for Air Nostrum (via ACMI). I now fly the A320, not the 737, and in freedom units, so forgive me for any mistakes.
It sounds like they were planned to fly for 2:30, and ended up flying 3:26 after holding at FL350. Guess that holding would have burned around 2000kg, and they landed with 1120kg (questionably precise amount). So the plan was to land with around 3000kg. Alternate fuel would have to be at least around 800kg for either Ibiza or Mahon, and minimum was 1200kg. So they left the UK with about 1000kg extra.
Do these numbers sound about right?
If so they departed with less than 30 minutes extra fuel into questionable weather, and held over BCN at FL350 for over 30 minutes ( based on total flight time) and still decided to continue to PMI, knowing they would get there with adverse weather and no extra and less than alternate fuel.
Even if you agree with the concept of committing, that does not apply here. It would be different if they were holding a low altitude over an isolated airport, where the divert option would be unsure. They were holding at high altitude, and were right above an airport (with even more runways, not that that matters if there is weather.......), so definitely they had other options.
Typing with a drink in hand, in a comfy chair, firmly on the ground.

What's that song? Isn't it ironic?
 

The "authorities" also will be sitting, comfortably, with drinks, of perhaps coffee, maybe with biscuits while they examine what others did "in battle."

the armchair syndrome incorporated.

They had a successful outcome.

If they had a history of landing with less than final reserves then there should be
a firm bollucking (sp?) But an isolated event should be a lesson session.

Where has this idea come from that they continued knowingly to destination with adverse weather?

The CAA view may help:

https://publicapps.caa.co.uk/docs/33...e2019002V3.pdf


From a common sense view, if the weather is dirty all across the Balearic why would you waste your diversion fuel going somewhere that’s no better (I haven’t seen Ibiza or Menorca WX for that day), and in the 20 minutes or so it takes to get there having to recalculate, rebrief, consult checklists, inform Co, Cc, pax, and all the other stuff with a chance of dropping the ball when you can spend the time in the hold making sure you are giving plan A the best chance it has?

Meanwhile Spanish ATC is sitting quietly in the background hoping nobody brings them into this 'handbags at dawn' discussion....

Whilst I am no defender of what I've seen of Spanish ATC, let's wait and see what the investigation tells us.

SIA can give some lessons here 😊

https://avherald.com/h?article=50f11fc3&opt=0