The U.S. military has confirmed another Russian military aircraft was tracked while operating near the U.S. state of Alaska on Monday, the second such incident in less than a week.

North American Aerospace Defense Command (NORAD) said that it had “detected and tracked” one Russian military aircraft while it was operating in the Alaska Air Defense Identification Zone (ADIZ). The Russian aircraft remained in international airspace and did not enter U.S. or Canadian sovereign airspace, according to a NORAD press release.

Speaking to VOA on Wednesday, a NORAD official declined to identify the type of Russian military aircraft, adding that U.S. fighter jets did not fly out and intercept the aircraft in this instance.

The flight occurred as several planned large-scale military training exercises are underway in and around Alaska.

Last Thursday, U.S. F-16 and F-22 fighter jets intercepted six Russian aircraft, including TU-95 bombers, SU-35 fighter jets and IL-78 tanker aircraft that had entered the Alaska ADIZ. NORAD said the Russian aircraft did not enter U.S. or Canadian sovereign airspace.

The ADIZ is international airspace directly next to sovereign airspace “that requires the ready identification, location and control of all aircraft in the interest of national security,” according to NORAD.

“NORAD remains ready to employ a number of response options in defense of North America,” the command said.