NATO is bolstering its eastern flank following alleged Russian incursions. CNN joined a surveillance flight

After slowly taxiing towards the runway at NATO’s Geilenkirchen airbase in Germany, the pilots go full throttle and the decades-old E-3 Sentry surveillance plane screams as it gains speed and lifts off on its way to Eastern Europe.

After multiple recent incursions by drones and aircraft into NATO airspace, the alliance is beefing up its presence in Eastern Europe, to counter Russia’s threat.

NATO’s name for this mission is “Eastern Sentry,” and CNN was invited on an eight-hour surveillance flight over Eastern Europe, looking deep inside Russian and Belarusian territory to detect possible encroachment on NATO’s airspace.

The crew consisted of servicemembers from various NATO countries, including the United States, Canada, Denmark, Germany, the Netherlands, Portugal, Spain, Romania and Turkey.

“These missions, they mean a lot to us,” Lt. Col. Stephen Wahnon of the US Air Force told CNN. “When we’re patrolling these borders, they are our borders. So, it means a lot for us to be out here to defend our borders.”