gypseyjaney: I have had repeated API issues within MMB for the last year on four or five LH flights to the US. Interestingly not on any SH flights within Europe. I have spent some time on the phone with customer service and have been told about various systems at the airport that are not in synch with those on MMB. I have never been denied OCLI because sometime after the T-72 [but, critically, before T-24] the data that I know is in the MMB record does get "approved" [my words]. The phone calls I have had inferred that my US passport presents a challenge somewhere in API part of MMB where it is looking for a first US address on arrival but obviously doesn't ask me for it as it knows I am a US citizen. I'm not sure about this as there must be a huge amount of US citizens travelling UK-US who don't get this bug. I might also add that on my SH European hops I use my Irish passport. Quietly I wonder if the system is aware of that and a conflict is somehow showing up which makes API unhappy.

Have you always been able to OCLI in the end or are you prevented? Agreed, it is annoying to see the API alert every time you're in MMB but if it does resolve itself I guess one should have that glass of whatever and not stress too much. Many many many bugs in good ol' ba.com