DETROIT (AP) — The U.S. is making General Motors recall and repair nearly 6 million big pickup trucks and SUVs equipped with potentially dangerous Takata air bag inflators.

The decision announced Monday by the National Highway Traffic Safety Administration will cost the automaker an estimated $1.2 billion, about one third of its net income this year.

GM had petitioned the agency four times starting in 2016 to avoid a recall, contending the air bag inflator canisters have been safe on the road and in testing. But owners responded by accusing the company of putting profits over safety.

Takata used volatile ammonium nitrate to create a small explosion to fill air bags in a crash. But the chemical can deteriorate when exposed to heat and humidity and explode with too much force, blowing apart a metal canister and spewing shrapnel.

Twenty-seven people have been killed worldwide by the exploding inflators including 18 in the U.S.

It took the agency more than four years to arrive at its decision, which comes toward the end of President Donald Trump's four-year term.

NHTSA said in a prepared statement that it analyzed all available data on the air bags, including engineering and statistical analyses, aging tests and field data.

“Based on this information and information provided to the petition’s public docket, NHTSA concluded that the GM inflators in question are at risk of the same type of explosion after long-term exposure to high heat and humidity as other recalled Takata inflators,” the agency said.

The company has 30 days to give NHTSA a proposed schedule for notifying vehicle owners and starting the recall, the statement said.

GM said that although it believes a recall isn't warranted based on the factual and scientific records, it will abide by NHTSA's decision.

The safety and trust of those who drive our vehicles is at the forefront of everything we do at General Motors," the company said in a prepared statement.

The decision means that all Takata ammonium nitrate inflators in the U.S. will be recalled, NHTSA said. Earlier this year the agency decided not to seek a recall of inflators with a moisture-absorbing chemical called a dessicant. But NHTSA said it would monitor those inflators and take action if a problem arose.

In a 2019 petition to NHTSA, GM said the inflators were designed to its specifications and are safe, with no explosions even though nearly 67,000 air bags have deployed in the field.

But Takata declared the GM front passenger inflators defective under a 2015 agreement with the government.

In its petition, GM said that Northrop Grumman tested 4,270 inflators by artificially exposing them to added humidity and temperature cycling, and there were no explosions or abnormal deployments. It says GM has “established that worse-than-worst-case humidity exposure and temperature cycling will not cause inflator ruptures ... at any point within even unrealistically conservative vehicle service life estimates.”

Exploding Takata inflators caused the largest series of auto recalls in U.S. history, with at least 63 million inflators recalled. The U.S. government says that as of September, more than 11.1 million had not been fixed. About 100 million inflators have been recalled worldwide.

Most of the deaths have been in the U.S., but they also have occurred in Australia and Malaysia.

Drivers can check to see if their vehicles have been recalled by going to https://www.nhtsa.gov/recalls and keying in their 17-digit vehicle identification number.

The recalls drove Japan’s Takata into bankruptcy and brought criminal charges against the company. Eventually it was purchased by a Chinese-owned auto parts supplier.