"Is there a doctor on board?" is perhaps one of the questions most dreaded by people in the medical profession.
Yet doctors and nurses are constantly being asked to respond in emergency situations because they are, in theory, best qualified to help.
Dealing with the aftermath of a car accident, treating a heart attack victim mid flight or helping a passerby collapsed in the street - all are seen as part of a doctor's duty.
On 7 July 2005, a group of doctors preparing for a meeting at the headquarters of the British Medical Association in London's Tavistock Square heard a bomb explode. The no 30 bus had been ripped apart right outside their building.
Dr Peter Holden, a GP from Matlock, took charge of the carnage created by the terrorist's bomb. By coincidence he was also trained in immediate emergency care.
In his diary, written soon after the events of 7/7, Dr Holden recalls his feelings on that fateful morning: "I have trained for such a situation for 20 years - but on the assumption that I would be part of a rescue team, properly dressed, properly equipped, and moving with semi military precision.
"Instead, I am in shirt sleeves and a pinstripe suit, with no pen and no paper, and I am technically an uninjured victim.
"All I have is my ID card, surgical gloves, and my colleagues' expectation that I will lead them though this crisis."
Yet Dr Holden and his colleagues set about treating the injured and the dying.
Making do
His initial concern was to ensure that the area was safe and that the patients and doctors were safe. At any point another bomb could have gone off.
His next priority was to work out who to treat first, using a very rudimentary system of triage.
"It's not the people shouting and screaming and making noise you go to first, it's the quiet ones," he says.
With no access to fluids for another 40 minutes, the doctors had to concentrate on opening airways, controlling bleeding and treating the walking wounded.
Everything had to be done quickly. Very quickly. And these acts were to prove vital that day.
Dr Holden and his colleagues couldn't save everyone they treated in Tavistock Square on 7/7, but the GPs "instinctively understood they had to do the most for the most," he says.
Other colleagues wanted to do a perfect 'Rolls Royce' job, he remembers, but in emergency medicine "it's about making do and mending".
As vice chairman of BASICS, British Association for Immediate Care, Dr Holden says that most doctors are not trained to deal with emergency medical events.
But the public still expects a doctor to be able to handle an unconscious patient and deliver a baby wherever and whenever it occurs.
Medical people know they can't walk by on the other side of the road - it wouldn't be ethical - but they also have a job to cope with the emergency they are confronted with.
Often it means improvising.
Drinking straw
In 2001 two doctors, a professor of orthopaedic and accident surgery and a senior house officer, famously saved a woman's life on a flight from Hong Kong to London on which they were all travelling.
The woman had a collapsed lung and the doctors created their own chest drain using a coat hanger, biro and mineral water bottle.
There are many other stories of heroic life-saving interventions - and not just by medical personnel.
In April 2007, a pregnant woman's waters broke on a First Choice Airways plane flying to Crete from Manchester.
With the help of air stewardess Carol Miller, Alfie was born while the plane was in mid-flight, weighing only 1lb 1oz. He was three months premature.
His breathing was so poor that the resourceful and heroic Miller made use of a drinking straw to inflate his lungs. She then performed mouth-to-mouth on the baby and repeatedly massaged his heart until the diverted plane landed at Gatwick.
Would a doctor have coped in a similar situation?
Lost confidence
Dr Vic Calland, a clinical adviser to North West Ambulance Service, also runs BASICS courses for GPs, nurses and doctors on pre-hospital emergency care.
"Doctors can often be very nervous of performing their skills in front of an audience," he says.
GPs want to attend his courses, "because they have not worked in hospital recently and they have lost confidence in their skills," he explains.
"It's my job to reassure them that they do have the knowledge and tell them it's well within their grasp."
Dr Agnelo Fernandes, urgent care spokesperson for the Royal College of General Practitioners says that all GPs generally have an annual refresher course in resuscitation training, which also covers burns and trauma.
"Many GPs also have background in working in an A & E departments as part of their training. GPs are part of a team in surgeries and nurses are also trained to deal with life-threatening conditions," he says.
Too technical
New equipment is also helping save more lives in emergency situations.
A device designed with the military to treating someone with a punctured lung and another device for opening airways quickly and efficiently are "absolutely life-saving", Dr Calland says.
He also knows what it is like to attend major incident scenes with the ambulance service.
A motorcyclist's lower leg, which was already severely damaged in a road accident, had to be amputated at the scene. Using a scalpel and some anaesthetic, Dr Calland cut through the last bits of muscle and skin to finish the job.
The concern from those working in emergency care is that medical students are not being trained appropriately to cope in emergencies.
Dr Holden explains: "There's a danger that we are producing doctors who are too technical for our own good. The curriculum is more concerned with the touchy-feely stuff than the knowledge."
"In an emergency you want someone who knows their job, who can work from first principles."