I just flew BHD-LHR-EWR-ZVE with each segment operated by a different carrier (with the last segment with the Amtrak code-share trick), all on a CO ticket. As I had never flown something quite so complicated, there were quite a few details that I was worried/wondering about how they would work out. Well, everything worked out, but I figure I would share those details in case anyone is in the same boat in the future. BHD-LHR operated by BMI: According to the website, unless you are flying flexible economy or business, then you are required to check-in online or use the kiosks at the airport. As I only had a CO confirmation number I was a little worried how this would work. Turns out, two days before the flight I got an email from CO with the BMI confirmation code. As a side note, I had email access because I bought a prepaid O2 sim card and put it in my unlocked smart phone. I highly recommend doing this, if only for email and maps. Data will cost you 1 GPB a day. Unlike in the US, if you check-in online and don't have a printer you have to specify "I will pick up my boarding pass at the airport" or you will end up having to speak to an agent at the airport. It required a phone call for the agent to print my BPs, but he was able to print the LHR-EWR BP as well. Transfer at LHR: BMI and other star alliance carriers (including UA) are all in Terminal 1. CO is in Terminal 4. The transfer is painless, though not quick (maybe 15-20 minutes depending on the bus). The route from the gate to the bus is signposted well (follow the purple signs). There is one checkpoint where you have to show an onward BP or itinerary. If you have a CO flight number I would check beforehand if its operated by CO or UA. Some poor fellow who was flying to IAD with an LH ticket and a CO flight number made the trek all the way to T4 only to find out it was operated by UA in T1 where he had started. LHR-EWR on CO... uneventful. Transfer at EWR to Amtrak to New Haven: Took the Airtrain from the Terminal to the Rail Station. I've taken Amtrak from here before, but never as a CO codeshare. Unfortunately, the Amtrak QuikTrak kiosk was unable to locate my reservation. The gentleman behind the counter was able to help, but he needed my ticket number. If you take the Amtrak CO codeshare then I highly recommend making sure you have your ticket number (the one that starts with 005). I didn't, as it wasn't on the BPs printed by BMI, nor the itinerary I had printed out before the trip. The Amtrak agent had to call CO to get the ticket number to access the Amtrak reservation. Fortunately for me, he was also able to put me on an earlier train (I had allowed for extra time in Customs, but ended up breezing through). Hope this is helpful to other travelers. The miles from the BHD-LHR and LHR-EWR legs have posted (2 business days after the flights). The Amtrak leg has not (for which my confirmation email promised me 250 miles). And those 250 miles are important because my next trip will leave me 53 EQM short of 2P without them.