The NFL has approved a plan in which teams can wear alternate helmets with their throwback uniforms starting in 2022, according to league spokesman Brian McCarthy.

McCarthy tweeted Thursday that teams must tell the NFL of their plans for an alternate-color helmet for the 2022 season by July 31, even though they won't be used for another year.

The use of a second helmet was dropped in 2013 over concerns that wearing more than one helmet might not be safe for players. As those concerns have eased, clubs have lobbied for a second helmet because options for alternate jerseys were expanded in 2018, the league said in a memo sent to teams and obtained by The Associated Press and other media outlets.

The second helmet can be worn only with so-called classic, alternate or Color Rush jerseys, and all players must be fitted for both helmets before training camp, the league wrote in the memo.

But an additional helmet design would likely be most popular with throwback looks, which could include the Tampa Bay Buccaneers' white helmet with an orange buccaneer logo, the New England Patriots' Pat Patriot look and the Tennessee Titans' Oilers throwback.

The primary and alternate helmets must be the same make, model and size. The alternate helmets must be worn in practice the week of the game they will be used, if not before.

The NFL began allowing throwback uniforms to commemorate its 75th season in 1994. They gained popularity through the years before the limit of one helmet made alternate uniforms less enticing because of the difficulty matching the base color of the primary helmet.

The Associated Press contributed to this report.