Yes, Just in Time has it's problems because it typically does not allow for catastrophes. Of course, second sourcing is pretty common but requires time to get parts in-house and, when an event such as those occur, second sources will often not have enough product available to meet the requirements.
The industry standard "Just in Time" supply chain does not work with major disruptions like the one in Japan. I am surprised by the lack of 2nd sourcing of the air sensors and wondering why auto manufacturers did not insist on physically separate and possibly completely independent second sources for all key components. This is a basic failure of risk management 101. One may argue that "who would have expected this?" but that is not a valid argument; earthquakes in Japan (and elsewhere) are not unusual nor unexpected. Yes the magnitude was significant but then again not a 1 in a million type of occurrence. We should learn from this experience and develop contingency plans for any major production area or specialized part supplier.
Hitachi airflow sensors from japan is now in short suppy or not available so the vehicle manufactures globaly sorting to reduced production or halt the production. Now japanese manufactures needs to think and start their ancilary units in other countries for those products whih are marketed globally.