mid-checking or short-checking in reverse?
 

I'm looking at flying US-LON-XX R/T this summer (where a number of XXs yield cheaper fares than flying US-LON), and will need to check a bag, but on the return would prefer not to check my bag on my positioning flight to XX and on the return flight from XX to LON (depending on the length of the layover, I would leave it at the airport or at the hotel), but would then need to check it for the flight from LON-US. Possible?

Probably not. US outstations in particular do not like short checking bags.

If I understand you, you're asking if you can check a bag in at LHR when flying XXX - LHR - USA?

If so, then that's not a problem providing you manage the logistics of storing the bag somewhere fairly handy..

Myself and another FT member actually did this a couple of weeks ago, albeit travelling in F.

I had a RFS ticket LHR to INV, and a cash booking INV to LHR to EWR (and onwards to SJC via LAX after an overnight).

I checked in at the First desks, gave them both PNR's and told them I didn't want to take my bag to Inverness. I asked to check my bag straight onto the 2nd flight on the 2nd PNR.. The agent did this with no issues.

My travelling companion who checked in separately did the same thing (with the same flights) and had the same result.

Ah, have I misunderstood? If it is as you say then ignore my post OP.

If I have understood you right, you want to buy a USA-LON-XXX-LON-USA ticket. You want to fly USA-LON and then stay in LON for a bit. Then you want to fly LON-XXX merely to position to XXX, and then fly all of the inbound half XXX-LON-USA. Is that right?

On the assumption that this is what you want to do, then I wouldn't expect you to have any difficulty asking for the bag to be checked USA-LON only - after all, you are then stopping in LON.

In addition, it is possible to fly LON-XXX with no checked bags, XXX-LON with no checked bags, and then check in a bag at LON for LON-USA only.

However, you'd need to make sure that you have enough time after flying XXX-LON to collect the bag from wherever it is, and then get back to check it for LON-USA. In particular, you'd need to have contingency plans against the possibility that your XXX-LON flight is very delayed.

In theory it will work, but a lot of things can go sideways on this plan. The
least of which is that the carrier can decide to route you somewhere else on a connection. (Not likely, though) What's more likely is not having enough time at your LON connection.

Maybe you want to just bring your bags.

We do this regularly.

We fly (for example) LHR-DUB in the morning, stopping off a LHR hotel on the way to dump luggage. Then we start the ex-EU ticket in the afternoon, spend the night at the LHR hotel then fly to the US in the morning checking in the bags.

We've never had a problem.

Has anything changed regarding short-checking luggage ?

I'm seeing some posts saying it's no longer possible to check-in bags for segment2 before flying segment1 and other posts from people saying they do it regularly.

Is there a definitive answer ?

No, there is no definitive answer. Or if you want to be pedantic, the definite answer is you can't do it (except where you can!). Generally it works fine, but you really need to have Plan B - for which there are a dozen possibilities probably. The introduction on Airportr makes this a lot easier if LON is in the frame here.