The search for a new head of the Canadian Forces has slipped more than a month behind schedule.

CBC News has learned Gen. Walt Natynczyk, Canada's outgoing chief of defence staff, has already held his own going away party — a cottage barbecue attended by close staff held in June.

Sources tell CBC News the military was planning for a late July change of command ceremony to herald the appointment of a new chief.

But, now it seems there will likely be no decision until at least the beginning of September. And even that date might be optimistic.

Natynczyk is said to have extracted from the Conservative government the promise of a month's warning before the top general will be formally ushered out the door, and no such warning has yet been issued.

It's not clear what is causing the delay. But CBC News has learned the process to select a new chief of the defence staff has become more formal than ever before, with a selection committee interviewing a large number of contenders for the job.

This is the second time such a process has been used.

The selection panel that chose Natynczyk was made up of Defence Minister Peter MacKay, his deputy, and a group of senior bureaucrats including the clerk of the privy council, according to a source familiar with the process.

That panel invited several candidates for interviews, and made at least one recommendation to the prime minister.

Top military job more political now

It appears the same process is being used this time, but the process is now said to be much more under the control of the prime minister and his senior bureaucrats.

"This is the prime minister's CDS," the source said. "It's clear that he has to be very comfortable with the person who is in the job."

Prime ministers have not always expressed such interest.

In years — and decades — gone by, prime ministers have sometimes just rubber-stamped the appointment, based on the recommendation of their minister of defence.

Lt.-Gen. Stuart Beare, currently commander of all of Canada's overseas forces, is one possible pick for chief of defence staff. (Murray Brewster/Canadian Press)

But, over the years, the top military job has become more political and the person who wins the job is destined to be featured on the evening news, and a household name (former military chief Rick Hillier, for example).

This time around there are only a few contenders who, at first glance, appear to have the required charisma.

Lt.-Gen. Stuart Beare, currently commander of all of Canada's overseas forces, is one of them.

Beare is an artillery officer and a former paratrooper, who most recently served as deputy commander of NATO's police training mission in Afghanistan.

Lt.-Gen. Tom Lawson is an air force officer who impressed with his deft handling of media questions at news conferences during the war in Libya last summer. Lawson is currently deputy commander of the North American Air Defence Command in Colorado.

In both cases, these generals are relatively new to their high ranks.

Wildcard candidate a retired general

The commanders of at least two of the military's three services are also said to be on the shortlist, army commander Lt.-Gen. Peter Devlin and navy commander Vice-Admiral Paul Maddison.

It's believed the navy's strongest competitor for the top job — a position it hasn't held since 1997 — is Vice-Admiral Bruce Donaldson.

Donaldson is currently the vice-chief of the defence staff under Natynczyk. He also commanded all domestic military forces during the 2010 Vancouver Olympics, and the G8 and G20 summits that followed. Donaldson had previously served as the director of the strategic joint staff — a highly political job in the middle of every important issue and operation at the centre of national defence headquarters.

It's possible air force commander Lt.-Gen. André Deschamps has been interviewed but he's not said to be a serious contender. Deschamps would also come with political baggage, being the air force face behind the controversial decision to sole-source the purchase of the F-35 fighter jet.

The wildcard candidate is not even in the military.

Retired lieutenant-general Andrew Leslie was once believed to be a shoo-in for the job.

He's a highly respected former general who is well-liked across Ottawa and is charming when he appears on television and before parliamentary committees.

Leslie is also the grandson of two former defence ministers: Brooke Claxton and general Andrew McNaughton, who fought in the First World War, became a peacetime chief of the general staff and fought in the Second World War.

Getting Leslie back in uniform is challenging

Leslie was in the spotlight more than a year ago after issuing a blockbuster report on how to remake the Canadian Forces from top to bottom.

Andrew Leslie has retired from the Canadian Forces and getting him back into uniform could prove politically challenging. (Stephen Thorne/Canadian Press)

That report was well-received by politicians, but derided in some corners of the defence department. At the time, it was posited Leslie would be asked to remain in the military in order to become chief of defence staff and implement his report.

But Leslie has now retired, and bringing him back into uniform is politically challenging for the government — although not without precedent. General Jean de Chastelain held the top military job until 1993, and then served again from 1994-95 at the request of then-prime minister Jean Chretien.

But, in the case of Leslie, at least one senior government official has mocked the media speculation surrounding Leslie's primacy in the race.

There are other high-profile names that have been bandied about as possible successors to Natynczyk, including Maj.-Gen. Jon Vance, who commanded in Afghanistan, and another Afghanistan veteran, Maj.-Gen Mike Day, formerly Canada's most senior special forces soldier. But CBC News has been advised to rank these two generals as low on the shortlist — if they're even on it.

Much has been made in Ottawa about the predominance of army generals in the top job over the years. But one source familiar with the process that selected Natynczyk said too much was being made of that complaint. Although it's important to have an air force general or navy admiral in the top job at some point, it doesn't have to be this time, he said.

"It's not the most important factor."