U.S. prosecutors charged four Belarus officials with airline piracy over the diversion of a Ryanair flight last year that resulted in the arrest of a dissident journalist.

Ryanair 4978 was destined for Vilnius, Lithuania, on May 23 but was diverted to Minsk, the Belarusian capital, while in Belarus airspace. Belarusian authorities claimed the diversion was due to a bomb threat. 

In reality, they were seeking to detain an exiled dissident journalist whom the Belarusian government had accused of “fomenting ‘mass unrest,’” according to a copy of the indictment unsealed Thursday. 

Though U.S. authorities acknowledge the incident happened outside their jurisdiction, the presence of four Americans on board the plane made the diversion a violation of a U.S. law prohibiting aircraft piracy, according to the indictment. The law carries a minimum 20-year prison sentence.

The indictment, by the U.S. attorney’s office in Manhattan, said the grounding of the flight was orchestrated by four officials in Belarus’s security services and air navigation authorities. All remain at large. Belarus doesn’t have an extradition treaty with the U.S., and the officials likely could be tried in the U.S. only if they were arrested traveling to a U.S.-allied country.  

The U.S., the U.K. and the European Union have imposed sanctions on Belarus and several of its companies and business leaders, including Belaruskali OAO, a potash producer and one of the nation’s largest state-owned enterprises, as a result of the incident and a broader crackdown on political critics by the administration of President Alexander Lukashenko. 

Lukashenko has faced increasing U.S. and EU pressure over his brutal crackdown on widespread protests following disputed presidential elections in 2020. Russian President Vladimir Putin stood by his ally and has sought to capitalize on the crisis by pressing Lukashenko to accelerate economic and political integration between Russia and Belarus.

The dissident, Roman Protasevich, and his girlfriend have been held under house arrest since shortly after they were removed from the flight. Protasevich could face as long as 15 years in prison on the charges he faces in Belarus.

The case is U.S. v. Churo, 22-cr-38, U.S. District Court, Southern District of New York (Manhattan).