In a nod to President Trump, Brazil’s nationalist movement has adopted the stars and stripes. Now one flag could be the focus of an investigation involving the N.F.L.

© Victor Moriyama for The New York Times

The Supreme Court ruled in 1989 that burning an American flag is speech protected by the First Amendment. President Trump says it should be punished.

© Jenna Schoenefeld for The New York Times

The Air Force is phasing out its use of the symbol, which dates to its foundation in 1918. An official said that it had sometimes caused “awkward situations.”