Originally Posted by
BA6501
Not sure whether CAI would've ever been a valid origin anyway under the old rules - but moot point, as that lounge (well, shower rooms) has long closed. You'll need to wait for Dali to open. I take it this is the new IB route to CAI, which doesn't get back to MAD until 3:40am or so...
If you have Priority Pass, or wish to pay for access, the
AENA lounge in T4 main opens at 5am.
The AENA T4S Neptuno lounge is 24/7, from T4S one would have to be allowed through pre-passport security (as if connecting to another T4S flight), hang around in Neptuno till the other other lounges open, use the
other "LupineChemist door"
(post 844) to get back to T4S arrivals stream and proceed through passport control as per normal. If the alternative is nothing really between 0340-0500 maybe it's worth a try?