Nimrod aircraft was barred from refueling in midair Friday after a crew noticed fuel spraying into the plane's bomb bay during one such operation.
The aircraft landed safely and was being looked at by engineers, Britain's Ministry of Defense said. Air-to-air refueling was suspended while the military investigates.
Britain's fleet of Nimrods, some which entered service with the Royal Air Force more than 30 years ago, has been criticized as too old, and the planes' refueling system has been a past focus of concern.
Earlier this year, the planes were grounded after a dent was discovered in a fuel pipe.
The military set up a board of inquiry to investigate the deaths of 14 servicemen whose Nimrod crashed in Afghanistan in 2006. The military said that investigation was nearly finished.
Moscow is trying to stop Balkan countries from entering NATO. Greece eventually took measures against Russia, even though Greek Prime Minister Alexis Tsipras had earlier said that Russia was Greece's strategic partner
The Ukrainian government refuses to abode by its obligations, rejects a peaceful resolution of the conflict, and disregards its own people, the president said