We are on the other side of things -- flying TO LHR from Madrid tomorrow. Flights show all on time for tomorrow -- and some of today's flights to LHR are OK (or running a bit late).
I suspect Monday will be a bit less fraught -- but as a bit of a safety -- we repacked our carry on to include clothes for Tuesday as well.
We're unable to complete check in -- we get past the number of bags to check screen and going next returns an "unable to complete online checkin -- please check in at the airport). Since we are going to be checking bags and flying J -- I hope things work out OK tomorrow -- but frankly this is a serious case of messed up.
We'll be flying out of LHR on Thursday for the US and hope by then the outbound dust from LHR has settled.