Six US Air Force B-52 Stratofortress bombers are flying over all 30 NATO nations.
They are being accompanied by around 80 fighter aircraft from 20 other alliance countries.
Based at the 5th Bomb Wing, Minot Air Force Base in North Dakota, the B-52s arrived in Europe earlier this week, landing at RAF Fairford in Gloucestershire.
The Royal Air Force is also taking part in the 'Allied Sky' event.
NATO Secretary General Jens Stoltenberg said the event is to demonstrate the "powerful commitment" of the US to NATO.
It is also to show "allied solidarity in action", he added.
Cover image: Library image of a US B-52 Stratofortress (Picture: US Marine Corps).