Boeing Max 8 safety feature was an additional option

Standard  Boeing 737 Max 8 planes are not equipped with a angle of attack indicator or an angle of attack disagree light and cost extra. As the pilots of the doomed Boeing jets in Ethiopia and Indonesia fought to control their planes, in vain they lacked two essential safety features in their cockpits. Several airlines especially low-cost carriers like Indonesia’s Lion Air have opted not to buy extras as regulators don’t require them. Faulty data from the sensors on the Lion Air plane may have caused the system, known as MCAS to malfunction authorities investigating that crash suspect.

Boeing’s optional safety features, in part could have helped the pilots to detect any erroneous readings. One of the optional upgrades the angle of attack indicator displays  the readings of the two sensors. The other called a disagree light, is activated if those sensors are at odds with one another. Neither feature was mandated by the Federal Aviation Administration.