The U.S. and South Korea conducted a rare armed air force demonstration on Tuesday in response to North Korea’s recent missile launches, according to the ROK military, flying 20 fighter jets in formation over the Yellow Sea.

The joint exercise marks the second time this week that the allies have carried out a response action in reply to what Seoul has called DPRK “provocations.” The U.S. and South Korea launched eight missiles the day before, after Pyongyang fired a salvo of eight short-range ballistic missiles on Sunday.