Two years after passing legislation that would have required substantial cockpit changes in new versions of the 737 Max jet, Congress has agreed to give Boeing a last-minute reprieve, substituting other safety measures to address concerns that arose after two deadly crashes.
Boeing said the previous requirement would have been costly to carry out and confusing for pilots trained on other versions of the plane.
After 346 people died in two Max crashes, Congress passed a new air safety law in 2020. Among other things, that law set higher standards for pilot alert systems in any plane certified after Dec. 27 of this year. Few lawmakers or executives expected the legislation would apply to the Max, but delays in the Federal Aviation Administration’s certification of two new variants of the plane left Boeing scrambling in recent months to get the deadline extended or waived.
The government spending bill unveiled on Tuesday, which is expected to pass this week, keeps the requirement only for planes that first apply for certification after Dec. 27.
But the deal, which was proposed by Senator Maria Cantwell, Democrat of Washington, requires that Boeing make two changes to all Max models that some experts recommended after the crashes: installing both an additional system to measure the angle at which the plane meets oncoming air flow — also known as the angle of attack — and a way for pilots to shut off certain distracting stall warnings.
“Safety must always drive the day,” Ms. Cantwell, whose state is a major base of Boeing operations, said in a statement. “We should not rush the F.A.A.’s safety approval process. The safety-first alternative is much stronger than the no-strings-attached approach that was first offered. Passengers need to know that the entire Max fleet will be uniform and safer.”
The Max was banned globally after the second fatal crash in March 2019. That ban was lifted in late 2020, and two midrange versions, the Max 8 and Max 9, have been flying passengers again for about two years.
Two other versions, the Max 7 and the Max 10, await certification. The Max 7 is the smallest variant, offering maximum range, but with the fewest seats. The Max 10 is the largest, offering more seats but less flying range. The Max 7 is expected to be approved first.
Many airlines are content with the midrange options, but some have been eagerly awaiting the others. Delta Air Lines, for example, announced plans this summer to buy 100 Max 10 jets.
The congressional provision would give Boeing one year after the Max 10 is certified to add the safety enhancements to planes in production and three years to retrofit all Max planes in service. That span was chosen so that the changes could be made when the planes undergo routine maintenance. Boeing had already begun testing both safety improvements on the Max 10, with plans to make them able to be retrofitted to the other Max variants.
Boeing declined to comment on the provision on Tuesday. Earlier this month, Stanley A. Deal, president and chief executive of Boeing’s commercial plane unit, told Reuters that the company was “fully prepared” to support Ms. Cantwell’s proposal.
The end-of-year deadline was put in place to hold planes to modern rules governing pilot alert systems, which aim to better organize cockpit warning messages into a more centralized and descriptive interface. Boeing has argued that the current system on the Max has been used on its 737 predecessors for years without problem and that changing it now would be both costly and confusing for pilots switching between Max models.
Consumer advocates, families of those who died in the crashes and some safety experts disagree. In October, the Allied Pilots Association, which represents 15,000 American Airlines pilots, said it opposed sparing the new Max models from the provisions of the 2020 legislation.
Capt. Dennis Tajer, a spokesman for the union, said on Tuesday that the union still believed that the pilot alert system on the Max was “the right thing to do,” notwithstanding the safety requirements in the budget legislation.
The Southwest Airlines Pilots Association, which represents almost 10,000 pilots at Southwest Airlines, sided with Boeing this fall, saying that having to switch between alert systems would be confusing. Southwest, which operates an all-737 fleet, has nearly 200 Max 7s on order.