Sen. Edward J. Markey (D-Mass.) questions government transportation officials on aviation safety after two fatal Boeing 737 Max 8 aircraft crashes during a March 27 hearing by the Senate Commerce subcommittee on transportation and safety. (Joshua Roberts/Reuters)

Sen. Edward J. Markey (D-Mass.) introduced legislation Thursday that would bar aircraft manufacturers such as Boeing from charging additional fees for safety equipment that carriers may want but that the companies consider optional.

“For Boeing, safety features that could have saved 346 lives on two of their 737 Max 8s were yet another profit center, deemed optional like premium seats, extra bathrooms, or fancy lighting,” Markey said. “Aviation safety cannot be a luxury that is bought and sold for an extra fee, but a standard part of our fleets, ingrained in every bolt, sensor, and line of code on an aircraft. The ‘Safety is Not for Sale Act’ will ensure that all safety-enhancing equipment is never sold as a la carte add-ons.”

The legislation would require air carriers to adopt additional safety features and ensure all non-required safety-enhancing equipment is offered or provided to carriers without an additional charge.

Preliminary investigations into the crash of a Lion Air jet in October and an Ethiopian Airlines crash last month indicated that an automated anti-stall system, known as MCAS, may have been triggered by faulty data from an angle-of-attack sensor. Once engaged, the automated system pushed the planes’ noses downward, as pilots fought to gain altitude and control of the planes.

Boeing offered two instruments designed to alert pilots to possible malfunctions of those sensors, an angle-of-attack indicator and a warning light, but charged an extra fee to carriers that wanted them. Neither the Lion Air jet, which crashed into the Java Sea in Indonesia on Oct. 29, killing all 189 on board, or the Ethiopian Airlines plane, which crashed March 10, killing all 157 people aboard, were equipped with the instruments. The Federal Aviation Administration also did not require the instruments on the 737 Max jets.

In the wake of the two crashes in the span of five months, Boeing said it would offer both options free. It is not clear that the instruments would have prevented the crashes, but Markey and industry leaders said carriers shouldn’t have to pay for equipment that enhances safety.

“These senators are proposing legislation that is fundamental to confidence in air travel and the expectation that U.S. aviation is a world leader in aviation safety,” said Sara Nelson, international president of the Association of Flight Attendants-CWA, AFL-CIO. “Our lives and our jobs depend on the core principle that safety is priceless, just like every soul on the plane.”

Joe DePete, president of the Air Line Pilots Association, said the group “applauds the introduction of the Safety Is Not for Sale Act, a bill that would make additional safety information available to airline pilots in the cockpit and provide airlines with more safety data about the equipment they operate, while also making onboard safety enhancements easier to acquire.”

At a recent Senate subcommittee hearing on aviation safety, Markey repeatedly pressed Daniel K. Elwell, acting head of the Federal Aviation Administration, on why the agency allowed Boeing to charge extra for certain types of safety equipment.

Elwell said the FAA requires manufacturers to include all equipment necessary for the safe operation of the aircraft. The agency did not view the instruments in question as critical.

Boeing also maintained the plane could operate safely without the angle-of-attack indicator or the warning light.

“All aircraft delivered by Boeing and certified by the FAA are equipped with all critical safety features necessary to operate the plane safely,” the company wrote in response to a letter sent by Markey regarding the charges.

“This equipment is standard, and it does not cost extra,” the company wrote.

Markey said the instruments would have at least alerted pilots that one of the sensors may have been malfunctioning.