WASHINGTON — The Supreme Court has rejected challenges to the estimated $1 billion plan by the NFL to settle thousands of concussion lawsuits filed by former players.

The court’s action on Monday clears the way for payouts to begin to former players who have been diagnosed brain injuries linked to repeated concussions.

The settlement covers more than 20,000 NFL retirees for the next 65 years. The league estimates that 6,000 former players, or nearly three in 10, could develop Alzheimer’s disease or moderate dementia.

Players could receive up to $5 million each in the case of severe brain trauma.

Some former players and relatives of players who have died objected to the settlement.