IAD to MUC to LHR : Will I go through passport control twice in Munich?

Immigrations and Customs in London + Immigrations and Customs in Munich.

When you fly into Munich directly from the US, you deplane into the upper (?) level of Terminal 2, which is the international level. In order to leave that level you have to go through passport control in the middle of the level. If your flight to London (which is outside Schengen) is on Lufthansa, it probably also leaves from the international level, so you don't have to go through passport, you just stay on that level.

However, if you have to pick up your luggage and recheck it to London, you will have to go through passport control to leave the level and go to the baggage retrieval. If your flight to London is on an airline other than Lufthansa or it's alliances, you will probably have to leave the level to go to Terminal 1.

Technically you are not entering the Schengen area when transferring from the US to a non-Schengen country like the UK. So no passport control in MUC.

SLA, I see a British Air flight to London leaving from T1-A. Is there a way to get from the international level of T2 to T1-A without going out of Schengen? I think there is a bus from T2 to T1, but I don't know if it is secure non-Schengen.

Lee, that bus operates in the safe (airside) area. There's a non-Schengen to non-Schengen bus and another one for intra-Schengen connections. Just follow the signs "transfer bus to terminal 1" or vv.

There's a non-Schengen to non-Schengen bus

Interesting. Somewhere in the US there is a bus between secure areas in terminals but when you arrive at the new terminal you still have to go through security because they are afraid someone will jump on the bus between terminals.

Just curious- how could that happen if those areas are secure. Usually, where the buses go there are only airport ground employees. How could anyone else jump on? Which airport?

You cannot just jump on that bus. First of all, there are separate buses for intra-Schengen and extra-Schengen transfers departing from different gates. That gates are locked and are unlocked only when the bus has arrived. Secondly, the bus does either the intra- or the extra-Schengen transfer, there is no intermediate stop at the other door.

From the airport web site:

If your luggage is checked through for your connecting flight, you can use the shuttle that travels between the two terminals. The service is free of charge. Please follow the signs in the terminals.

More precisely:

From Terminal 2 non-Schengen you take the bus at gate H (signposted) and leave it at gate C08 in Terminal 1.

BTW, for flights to the US, there is an additional passport / security check immediatly before the gate.

Somewhere in the US there is a bus between secure areas in terminals but when you arrive at the new terminal you still have to go through security because they are afraid someone will jump on the bus between terminals.

I wouldn't be surprised if that was the case somewhere in the US. I just took a bus last week when changing planes in Munich, and I thought of that possibility, then realized it was absurd, because someone would have had to have breached airport security already to have gotten to that point.

In the US, O'Hare has, busses from domestic to the international terminal. Unless something's changed there since last summer you DON'T clear security again upon arrival at the international terminal.