RAF pilots are conducting joint air policing missions in Estonia alongside the German air force for the first time.
It comes as the UK prepares take over from Germany to lead the Nato mission in Estonia, which borders Russia.
Royal Air Force and German Air Force Typhoon jets will take part in the first of their kind "integrated" missions, as the Defence Secretary praised the demonstration of Nato "unity".
Around 300 RAF personnel are in Estonia as the UK gets ready to lead the Nato air policing mission - protecting Nato skies in the area - for four months from April.
The Russian invasion of Ukraine has reignited concerns in border states, including Estonia, about Vladmir Putin's ambitions and his next steps.
Defence Secretary Ben Wallace said: "Our RAF personnel in Estonia are undertaking a vital role, ensuring the security of Europe’s skies and bolstering Nato’s presence in eastern Europe.
"Joint operations of this kind, demonstrate the strength and unity of the Nato alliance and our shared resolve to maintain peace and security across the region."
Wing Commander Scott Maccoll, commanding officer of 140 Expeditionary Air Wing, said: "Today marks a great 'first' for our two Air Forces. We have been working together for some time and the level of cooperation has now reached a new level.
"It continues to be an absolute pleasure to work with our German allies on all aspects of our mission – from maintenance and operation of the jets to planning and logistic activities."
"What better way to demonstrate the strength and unity of the Nato Alliance, than through successful, shared operations such as this?"
The MOD said that the mission formed part of the UK's commitment to Nato member Estonia.
Lieutenant Colonel Christoph Hachmeister, the German Detachment commander, said: "Working together with our allies from the Royal Air Force in a live mission is what we have been looking forward to since we started this mission.
"Now we can demonstrate interoperability in these difficult times to protect our Baltic partners and Nato's eastern flank.
"The many years of good practice in working together will be the baseline for a successful cooperation."
Shadow defence secretary John Healey said his party's commitment to Nato co-operation with allies like Germany is "unshakeable", as he warned of the danger of cuts to defence projects.
He said: "Our RAF pilots will conduct these welcome exercises with total professionalism.
"But the Conservatives' mismanagement of defence projects such as Wedgetails and cuts to military transport planes are leaving the UK's Nato obligations in doubt.
"Labour in government would apply a 'Nato test' to major defence programmes to ensure our Nato commitments are fulfilled in full."