A senior RAF officer has told BBC Scotland he fears lives will be put "at risk" by the MoD's decision to withdraw Nimrods from operations.
The RAF will bid farewell to the aircraft at the Kinloss base in Moray on Friday when personnel and families will commemorate the role of the MR2.
It is due to be replaced operationally by the MRA4 in the autumn of 2012.
The MoD said the Nimrod's work would be carried out "by a variety of different aircraft" in the interim.
Some experts claim that the MoD proposals to fill the gap do not stand up to scrutiny.
They say the C130 Hercules transport plane which may be used to carry out some of the Nimrod's maritime missions does not have the capability.
Earlier this month, a Nimrod from RAF Kinloss took part in a rescue mission more than 200 miles south west of Cork in the Republic of Ireland, after a merchant navy seaman received serious head and spinal injuries.
The Nimrod helped provide "top-cover" for the helicopter crew from RAF Chivenor, and guided them to the ship, the Montreal Express.
But an RAF officer said that without the Nimrod's involvement the helicopter crew's lives "would have been put at risk".
He said: "The Hercules does not have proper maritime radar, their crews are not trained in search and rescue, they don't train regularly on doing visual searches at sea, and the do not practice dropping life rafts.
"These are special procedures necessary to save lives."
'Tasked as appropriate'
The RAF source said: "It is unfair that we put them in that position with no top cover.
"We have never lost a helicopter in hover, but we can't budget on the fact that it won't happen. I think we are putting helicopter crews at increased risk."
Aviation journalist and Nimrod expert Jon Lake said the withdrawal of the Nimrod this month was "ridiculous".
He said: "It is grossly irresponsible of the MoD. There is plainly not going to be just a capability gap but a capability chasm.
"The C130 can only do a fraction of what the Nimrod can do, and it is a cynical cost-cutting measure which will undoubtedly risk lives."
A spokeswoman for the MoD said that the work of the Nimrod would be carried out "by a variety of different aircraft, fixed wing and helicopters, which carry out the role that the Nimrod currently does".
She added: "They will be tasked as appropriate."
The new Nimrod MRA4 is due to arrive at RAF Kinloss in July for training purposes but will not be in operational service until autumn 2012.
Dozens of jobs have been lost at RAF Kinloss due to the withdrawal of the present Nimrod, a year earlier than originally planned.
The base is a major local employer and generates millions of pounds for the Moray economy.
Highlands and Islands Enterprise (HIE) has vowed to help.
Local SNP MP Angus Robertson praised the service personnel at the Moray base.
He added: "I am concerned that search and rescue operations may now not have the same capabilities until the replacement Nimrod MRA4 aircraft are introduced at RAF Kinloss.
"The Ministry of Defence must introduce the new Nimrods as a priority and ensure the appropriate capabilities are available to search and rescue as well as military operations."