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.