A Russian military jet made an unannounced trip to North Korea late Tuesday night, according to flight tracking services, the first known Russian flight since the two countries signed a mutual defense treaty last month.

The Russian Air Force Il-62M passenger plane (tail number RA-86561) departed from Moscow at around 12:10 a.m. KST on Tuesday and landed at Pyongyang’s Sunan International Airport at 9:12 a.m., aviation tracking websites Flightradar24 and FlightAware show.

Unlike many other Russian aircraft that carried out secret flightsto North Korea in recent months, the Il-62M maintained a relatively consistent radio signal en route to Pyongyang