The Detroit Exodus quickened after the racial riots. There was a police unit enforcing the racial oppression (STRESS). It was disbanded after a certain event:

The Detroit Exodus quickened after the racial riots. There was a police unit enforcing the racial oppression (STRESS). It was disbanded after a certain event: Southern Airways Flight 49 hijacking. 3 individuals, intimidated by the local Detroit government decided to take matters in their own hands: hijacking a plane (which was common up to the ~70's, since people were allowed to bring their weapons on the plane, back then the reasoning was that its more cost effective to deal with zest-for-life hijackers in the air), but not just hijacking a plane, they threatened to crash it into an Oak Ridge nuclear reactor (or more plausibly the surface storage). After a few back and forths they got a few million, some bullet proof vests and some parachutes. At some point a gun was fired and one of the pilots got hit in the arm. They tried to land in Cuba but were sent back by Fidel Castro (accepting these highjackers was figuratively radioactive), after refuel and some more flying around they tried landing in Cuba again. This time they were allowed to land, but then immediately arrested and went to prison in Cuba for ~7 years, then extradited to the US, sat in prison for another ~7 years. Shortly after this event: the STRESS police unit was disbanded, US airports finally installed metal detectors and X-ray scanners. According to interviews the hijackers were willing to die and were serious about the threat to crash the plane and cause release of nuclear materials if their demands were not met. Were they civil rights activists or violent terrorists? That is a false dilemma, one can be both at the same time.