'If they already have a good idea about aviation, they will progress much quicker.'

The full training programme takes five to six years, significantly longer than a college degree. It begins with about 18 months of familiarisation and courses in Hong Kong.

Groups of trainees are then sent to a flight school in Melbourne, Australia to learn how to fly small aircraft and, time permitting, to obtain a private pilot's licence.

Next, they head to Bournemouth in Britain to complete a 14-week air traffic control course. This not only gives them technical expertise, but also provides further exposure to an overseas environment and ensures their English - the language of the skies - is fluent.

On returning to Hong Kong, the next step is to complete the local training needed to gain a licence, a first rating, and promotion to air traffic control officer Grade 3.

At this stage, trainees are already specialising in either aerodrome control or area control. One is to oversee runway movements and all flights to a few miles out; the other involves everything happening in Hong Kong's designated international air space.

That extends roughly 300 nautical miles to the south and southwest, about 200 nautical miles eastwards, and north up to the border with the mainland.

'It is a big piece of air space to look after,' Mr Hong said, adding that it took constant co-ordination with Guangzhou, Taipei, Manila, Sanya, Macau, Zhuhai and Shenzhen.

'Each centre has its own airspace and when an aircraft is at the border, we transfer control.'

This involves confirming information about an aircraft's flight number, assigned radar code, altitude, and the time and point it will leave or arrive in Hong Kong airspace. This is done by voice, rather than on-screen messages, and the aircraft will also switch its radio frequency to communicate on the 'receiving' centre's standard frequency.

In-house Civil Aviation Department instructors conduct all local training. This consists of classroom teaching, simulator sessions, examinations and extensive on-the-job training which usually lasts five to eight months.

Individual instructors supervise every move a trainee makes when on duty until they have reached the necessary level of competence. The objective is to provide intensive coaching and allow early responsibility, so that people learn as fast as possible. Obviously, an instructor who spots or senses an incorrect move will jump in immediately to prevent any mishap from happening.

'We are trying to shorten this period, while still giving all the training required,' Mr Hong said. 'We closely monitor progress, and the instructor must confirm that someone is good enough to perform solo duties.'

Along the way, trainees also learn the procedures and protocols for liaison with ground services, apron control and the meteorological office. If conditions are bad, one of a controller's key tasks is to talk to the pilot about how to fly around, go over or otherwise bypass a weather system. The final decision, however, rests with the pilot.

Subsequent career advancement depends on performance and follows civil service grades and conditions.

The Civil Aviation Department has close to 250 controllers, but plans to recruit about 15 this year to cope with the forecast increase in traffic volume. Applicants must be Hong Kong permanent residents and are generally university graduates, although the requirement is a Form Seven education. Prior to acceptance, it is necessary to pass an aptitude test and a series of interviews designed to identify candidates who think logically, can multitask, show common sense, are time conscious and can respond correctly under pressure.

'It is definitely a high-stress job,' Mr Hong said. 'Therefore, it is a minimum requirement that for every two hours on duty, someone has at least a 30-minute break. On a busy day, it might [be] one hour on and then half an hour off.'

Controllers work a shift pattern based on a 10-day cycle. This gives them a mix of early, late and overnight shifts, as well as sufficient time to recuperate.

In a previous recruitment exercise, there were more than 4,000 applications, although ultimately just 17 were hired.

'The job attracts quite a number of youngsters, but it costs the government more than HK$1million to train up a controller,' Mr Hong said.

'That's why we have to be very choosy. Candidates have to impress us and convince us they are suitable for the job.'