Principal Investigator Status
At MIT three categories of people have automatic Principal Investigator (PI) Status: Faculty, Senior Research Scientists (SRS), and Principal Research Scientist (PRS). In order to be a PI when holding any other appointment at MIT, the individual's Department Head must request and receive permission from the relevant Dean for that individual to be a PI on a specific project. MIT requires that anyone beyond faculty, SRS, or PRS must provide confirmation of approval from their Dean for PI status for each protocol application (there is no blanket PI Status).
See MIT Policies and Procedures: http://web.mit.edu/policies/5/index.html