All UK military Nimrod MR2 aircraft have been grounded as a precautionary measure after a routine safety check uncovered a dent in a fuel pipe.
Some Nimrods have already been cleared, the MoD said
The decision was taken in the last 48 hours after checks on one aircraft, the Ministry of Defence has said.
The fleet was grounded while the issue is investigated but some of the aircraft have already been cleared.
It said an inquiry into the crash of an RAF Kinloss-based MR2 in Afghanistan in September should not be pre-judged.
The 12 air force crew, a Royal Marine and a soldier were killed on 2 September when the MR2 came down near Kandahar after a reported technical fault.
The Nimrod was designed as a sea patrol and anti-submarine aircraft and entered service with the Royal Air Force in the UK over 30 years ago.
In the early 1980s some RAF Nimrods were upgraded from the original MR1 design to the MR2, the main roles of which are sea surveillance, anti-submarine warfare and support for search and rescue operations.
Nimrod MR2s fly mainly from RAF Kinloss in Scotland, although a programme to replace them with an up-dated version - the MRA4 - is under way.
The MoD said investigations were ongoing "but some of the aircraft have been cleared of this problem and we expect others to follow shortly".
Checks were carried out on the fleet after the September crash and the Nimrod MR2 has continued to fly operations in Afghanistan and Iraq.
Its cause is currently being investigated by a Board of Inquiry.
Fifteen Nimrod MR2s are based at RAF Kinloss.
Scottish National Party MP Angus Robertson, whose Moray constituency includes the base, voiced concern at the latest development.
"It is the correct decision to put the safety of the Nimrod crews first and all necessary checks must be completed before flight operations are resumed," he said.
"This news underlines the need to finalise the replacement of the current Nimrod aircraft with the new generation of aircraft as a matter of priority."
Graham Knight, whose son Sgt Ben Knight died in the Afghanistan crash, said: "This is at least the third time they have grounded the fleet since the crash and makes me worry that it will happen again to some poor crew.
"It is not as if this is an unconnected fault as it was thought at the time a break in the fuel pipe could have caused the aircraft fire in Afghanistan."