If there is an emergency on board an aircraft, there's no place for hope; the lives of hundreds of passengers can depend on the training, quick thinking and cool-headedness of an aircraft's cabin crew.

Cathay Pacific's 4,300 flight attendants, for example, are well trained in such things as personal grooming and inflight service. But much of their training is, in fact, focused on dealing with far more weighty situations.

Situations which no airline likes to talk about, but which they must be ready for; illness and emergency evacuation of the aircraft during crash landings, either on land or sea.

Of the initial six-week training period which all Cathay cabin crew must undergo, 11 days are devoted to intensive safety training at CX's Flight Operations Safety Training School at Kai Tak.

Founded in 1975, the Safety School began with just three instructors; today it boasts seven classrooms and full size cabin mock-ups for a Boeing 747 and an L1011 Tristar; its present 19 staff train nearly 800 new flight attendants each year.

The safety instructors themselves must receive 12 months of intense training and be approved by a Flight Operations Inspector of the Civil Aviation Department before they can be certified to teach.

Because Cathay receives 25,000 applicants for the few hundred cabin crew openings each year, the recruits who survive the initial selection process to arrive at Safety Training School are already considered top quality individuals.

It is at CX's Flight Safety School that trainees are taught to deal with a large number of situations which you will never see on those charming television commercials.

The most common problems encountered are simple illnesses such as air sickness or nose bleeds.

Should more serious medical emergencies arise, senior pursers always first ask if there is a doctor on board; if not, the cabin crew are fully trained in first aid and to deal with heart attacks, epileptic seizures, insulin shock of diabetics and even unscheduled births.

Every CX aircraft carries a sealed doctor's kit containing medical equipment and 25 drugs.

At the Safety Training School cabin crew are also trained to become intimately familiar with detailed evacuation procedures for each of the different types of aircraft used by Cathay; the emergency opening of the air-lock doors, the deployment of inflatable escape slides and the possibility of fires.

In the event of a crash, time is of the essence in getting passengers out safely. Thus Cathay's safety training manual notes that ''in conditions of emergency, courtesy must be dispensed with''.

Using films and videos of actual crash landings, flight attendants learn the likely effects of a hard landing on an aircraft, as well as ways to calm passengers. Many things must be quickly considered, crucial decisions which passengers never consider.

For example, if an aircraft's nose gear is destroyed on impact, the rear of the aircraft may be pitched at a high angle meaning that the exit doors will be too steep to safely use the standard rubber escape slides.

In a matter of seconds cabin crew must evaluate the situation and decide which escape doors to use.

They must issue instructions, calmly and clearly, to passengers in at least one language. Cabin crew must also take into consideration elderly people and small children, who may easily panic.

Trainees are taught how to deal with passengers suffering from oxygen deprivation, and how to move injured or handicapped passengers out of the aircraft quickly but safely.

''Before our cabin crew finish their training here,'' says Newton Zah, chief instructor at CX's Safety Training School, ''they will go down that rubber slide at least 40 times, so that they know exactly what it's like in a real emergency.'' ''The secret to training people for something that we all hope will never happen,'' says Cathay's manager for ground training, Brian Almond, ''is drill and practice, over and over until it is second nature. We also bring all cabin crew back here every year and go through a simulated evacuation.'' Though airlines may be fiercely competitive in their marketing and pricing, when it comes to passenger safety, they are keen to pool their knowledge.

''We've visited British Airways, Lufthansa, Singapore Airlines, and they've sent people to look at us and we've compared notes,'' said Mr Almond.

After each segment of the course is completed, there are both written and practical examinations, until the trainees are fully confident in themselves to handle even the most unexpected incident or accident.

Statistically, the least likely emergency to be encountered by an aircraft is a landing over water.

Still, because the possibility exists, CX cabin crew are trained to handle ''ditchings'' in a outdoor pool at Kai Tak. Here they are taught to handle a 42-man rubber raft in a rolling sea.

They're also made familiar with the use of de-salting kits, the setting up of sea anchors, the use of radio beacons, how to repair leaking rafts, how to treat sunburn and seasickness and hypothermia. They are even instructed in the proper way to board rescue helicopters.

Yet another aspect of cabin crew training involves the risk of hijacking and hostage-taking.

Most details of such training is kept confidential for obvious reasons, but cabin crew are instructed by Cathay's special security officers on how to spot suspicious-looking people, how to deal with bomb warnings, drunken or unruly passengers, and hostage situations.

So, the next time you look at your cabin attendant, remember that she knows much more than which wine goes best with your veal. You're looking at someone who might well save your life in an emergency situation.