Two Boeing jets that crashed in Ethiopia and Indonesia each lacked a pair of cockpit safety features that the plane manufacturer charged extra for.

The systems might have helped the pilots as they struggled to control their planes, aviation experts said. Lion Air Flight 610 crashed in October killing 189 people, and Ethiopian Airlines Flight 302 went down on March 10, shortly after takeoff from Addis Ababa, with the loss of 157 lives.

Both Boeing 737 Max aircraft were new but did not have an angle of attack indicator, which shows how much the nose is tilted.

They also did not have an angle of attack disagree light, which is triggered if other sensors are giving conflicting information, the New York Times reported.

Such safety features were not required on new planes by the US Federal Aviation Administration, and Boeing charged a fee to have them put in if an airline requested them. Lion Air and Ethiopian Airlines had opted not to.

Boeing has now announced the angle of attack disagree light will be free on new 737 Max planes.