We know that it has false-activated at least 3 times, and each time has been a few minutes after takeoff. This is because if the sensor fails on the ground, MC

We know that it has false-activated at least 3 times, and each time has been a few minutes after takeoff. This is because if the sensor fails on the ground, MCAS will always activate a few minutes into the flight, when the flaps are retracted, because the rule that activates it is disabled when the flaps are down.