The doomed Boeing jets in Ethiopia and Indonesia lacked some safety features in their cockpits because the company charged extra to install them. But now, after the crashes and 737 Max jets being grounded around the world, Boeing says one of those features will come as standard on new models. Boeing’s optional safety features could have helped the pilots detect erroneous readings that experts believe may have been involved in the planes’ failures, The New York Times reports. One previously optional upgrade, called a disagree light, is designed to activate if a plane’s sensors are giving contradictory readings. That will now be added to the planes free of charge. Another optional extra, called the angle of attack indicator, displays the readings of two sensors—but that will still cost money to install. Neither feature is mandated by the Federal Aviation Administration. “They’re critical, and cost almost nothing for the airlines to install,” said Bjorn Fehrm, an analyst at the aviation consultancy Leeham. “Boeing charges for them because it can. But they’re vital for safety.”