Russian bombers may be flying nuclear strike drills over the Atlantic Ocean and North Sea, current and former U.S. Air Force officers believe. At the very least, these officers tell The Daily Beast, the Russian Air Force is aggressively probing what NATO calls European airspace in an effort to gauge the reaction times of the western alliance’s defenses.

Since Oct. 28, NATO air defenses have detected and monitored four groups of Russian combat aircraft over the Baltic Sea, North Sea, Atlantic Ocean, and Black Sea. Norwegian F-16 fighters intercepted one particular group of Russian aircraft on Oct. 29 that included four, nuclear-capable Tupolev Tu-95 Bear H strategic bombers and four Ilyushin Il-78 aerial refueling tankers. Once intercepted, six of the Russian aircraft headed for home while the two remaining Tu-95 bombers continued southwest, parallel to the Norwegian coast, before eventually turning back towards Russia.

The giant, propeller-driven Tu-95 is a launch platform for the 1,600 nautical mile range Raduga Kh-55 nuclear-tipped cruise missile. The weapon carries a 200-kiloton nuclear warhead; by comparison, the bomb that destroyed Nagasaki was a mere 21 kilotons. Some active-duty and retired U.S. Air Force officials told The Daily Beast that the Tu-95s might have been flying to certain predetermined launch points for their nuclear missiles.