LTNman
I think what you are looking at will eventually be a floor section of the station.
Rather than “ cut and cover “ this is more “ cover and dig”
I think you will find this section is on hydraulics allowing the underneath to be dug out, when this is done the whole section will be lowered to become the floor.
Possibly they will do this with another section using a digger and conveyor system to remove the soil.

Think we need Constuctors Input to confirm but it looks impressive.

I am curious as to which way they will excavate, it’s looking like towards taxiway delta but I may be wrong.
Keep an eye out for a second section!
At least they will be able to work underground and not be exposed to the elements, could this be their thinking as winter is coming?

I live 50 miles away so I am curious but not that curious I would drive there.
Like many I rely on LTNman for the updates.

I have no details of this contract so here is my calculated guess. This layer of concrete appears to have been laid to a very high spec. I think it will be a temporary layer immediately under the roof slab. If so the next work will be to lay a membrane which will act as a debonding layer to the roof slab concrete. After the membrane will come the reinforcing bars, lots of them will be fixed. The roof slab thickness will be 800- 1000 mm thick. The roof slab will also act as a horizontal column holding up the piles. Piles, concrete or steel, can only hold up soil to about 3m deep freestanding. Over that depth you need propping, called temporary works. My guess is that this dig will be 7m deep. The structure being formed is a box or an n shape. Once the roof slab is formed excavation inside the box will occur including the concrete you can see today. A very efficient method of construction. The next few days will be interesting. Hope I am right.

Constructor,
Many thanks for your input, looking forward to the updates from LTNman.

Yes that's exactly what I would do at least you would get a better idea as to what is happening rather than guessing.

As much I enjoy the updates and photos provided by LTNman and I really do honestly and I'm under the impression that he is local to LTN and I'm not sure if he actually works at the airport but the amount of time that he does spend at the airport taking photos personally I would be asking for as much information as possible from the contractors onsite regarding developments at the airport rather than making wild guesses.

There has to be an actual reason behind the laying of this concrete!

Go on LTNman next time your at the airport doing your next photo update go down and ask the contractors what's going on, because we all want to know now :-)

Oh and whilst you are at it, a comment from the airport operator about Taxiway Foxtrot :)

Easier said than done. There are 5 sets of contractors working at Luton who are working on 4 major projects. Then there are the dozens of subcontractors who are all doing their own thing so it is not always straight forward who is doing what. The projects are being carried out behind secure fences or in the case of the DART behind hordings. I am inclined not to loiter around a turnstile for long periods like a roving reporter hoping that I speak to an individual who has an oversight of the big picture.

Saying that I do actually have a senior contact for the principal contractor so I will send him an email and ask the question.

As for the rest of the DART outside the airport boundary work has recently started on the earthworks for the bridge that will cross the A1081 on the Parkway side. The steelwork for the bridge will be assembled on a pocket of land opposite the Ibis hotel and then taken to site. The span will be 72m long as it will have to cross a dual carriageway and at the same time the beginnings of the sliproad to the airport which is also two lanes.

Also I only take photos when I am in the mood and when there are enough changes to warrant them. With so much going on at the moment the frequency has gone up so it is a bit of a balancing act not to over do them here.

Finally guessing is half the fun so just think of it as a rumour.

Hi , you will have no problems.
The dual carriageway upgrades have all been completed now .
There are two Ibis hotels now , but they are pretty much opposite each other.

Talking of hotels the Courtyard by Marriott has now opened. The hotel rooms were premade in Eastern Europe and craned into position. The airport now has 6 hotels if the hotel by Parkway is included.

London Night Closures: Dark Future? | NBAA 2018 content from Aviation Week

I I'm sorry to say that I think that you may be the only one that's surprised by this!

Why not use LTN above the sign instead of LLA this can be very confusing for passengers from countries that use the code of the airport over the airport name this is a big pet hate of mine.
you wouldn’t fly to JFK and see NYA as a code or what can be conceived as a code.

I still don’t understand why an International Airport wants to brand away from its designated IATA code and brand itself using another Airports code LLA is the code for Luleå Airport (LLA) in Sweden.
If an unsuspecting passengers Google’s LLA the top results show Luton Airport it is not inconceivable the someone could end up in LTN expecting to land at LLA.
Is it even legal to Brand under another Airports code ?