You have only to read the correspondence columns in the specialist business travel magazines each month to see what a fashionable occupation it is to complain about airline services. Some people seem to enjoy writing letters of complaint so much that they make a profession of it. They complain at the slightest hiccup and write long letters detailing every flaw, claiming huge sums in compensation and threatening legal action if it is not forthcoming by return. But the fact is that no matter how much their inefficiency costs you in time, trouble, missed meetings, lost deals and overnight hotel bills, the airlines, in many cases, are not obliged to pay you anything. They are covered for most eventualities by their conditions of carriage, which are printed on the inside cover of the ticket. However, this is not to say that, in an increasingly competitive environment, the more enlightened airlines do not take their customers' attitudes seriously. Some airline chief executives take a personal interest in passenger complaints and have frequent 'purges', when they insist on seeing every letter of complaint that comes in on a particular day.

If you have a complaint against an airline that you cannot resolve satisfactorily, it is worth contacting the Air Transport Users' Council (AUC), CAA House, 45-59 Kingsway, London WC2B 6TE (tel 020 7240 6061, fax 020 7240 7071). The council is funded and appointed by the Civil Aviation Authority, but operates completely independently and, indeed, has frequently been known to criticise some of the authority's decisions. It has only a small secretariat and is not really geared up to handle a large volume of complaints, but it has had some success in securing ex gratia payments for passengers who have been inconvenienced in some way.

All the same, the council likes to receive passenger complaints because it is a useful way of bringing to light some serious problems, which can lead in turn to high-level pressure being brought to bear on the airline or airlines involved. Some of the subjects dealt with by the council in 1990 included European and domestic airfares, passenger safety, the pressure on airport and airspace capacity, overbooking and baggage problems.

Procedure

Here are some tips which may make complaining to an airline more effective:

Lost luggage

Most frequent travellers will, at some time, have experienced that sinking feeling when the carousel stops going round and there is still no sign of their baggage. The first thing to do if your luggage does not appear is to check with an airline official in the baggage claim area. It could be that your baggage is of a non- standard shape - a heavy rucksack, for example - which cannot be handled easily on the conveyor belt. If this is the case, it will be brought to the claim area by hand. But if your baggage really has not arrived on the same flight as you, you will have to complete a property irregularity report (PIR), which will give a description of the baggage, a list of its contents and the address to which it should be forwarded. Ask for a copy for yourself as you will need this - together with the baggage receipt - if you later want to claim compensation from the airline or from your travel insurance.

It is sometimes worth hanging around at the airport for an hour or two because there is always the chance that your baggage may arrive on the next flight. This sometimes happens if you have had to make a tight flight connection - you just squeak on to the flight but your baggage doesn't quite make it - although the current strict security requirements mean that normally a passenger and his or her baggage must travel on the same flight. But if there is only one flight a day there is no point in waiting and the airline will forward the baggage to you at its expense. In this case, ask the airline for an allowance to enable you to buy the basic necessities for an overnight stay - nightwear, toiletries and underwear, for example.

If your baggage never arrives at all, you should make a claim against the airline within 21 days. The airlines' liability for lost luggage is limited by international agreement and the level of compensation is based on the weight of your baggage, which explains why it is filled in on your ticket by the check-in clerk. The maximum rate of compensation at present is US20 per kilo for checked baggage and US400 per passenger for unchecked baggage, unless a higher value is declared in advance and additional charges are paid.

The same procedure applies to baggage that you find to be damaged when you claim it. The damage should be reported immediately to an airline official and, again, you will have to fill in a PIR form, which you should follow up with a formal claim against the airline.

Overbooking

Losing one's baggage may be the ultimate nightmare in air travel, but the phenomenon of 'bumping' must run it a close second. Bumping occurs when you arrive at the airport with a confirmed ticket, only to be told that there is no seat for you because the flight is overbooked. Most airlines overbook their flights deliberately because they know that there will always be a few passengers who make a booking and then don't turn up ('no shows' in airline jargon). On some busy routes, such as Brussels to London on a Friday evening, some business travellers book themselves on four or five different flights, so that there is a horrendous no-show problem and the airlines can, perhaps, be forgiven for overbooking.

The use of computers has enabled airlines to work out their overbooking factors quite scientifically, but just occasionally things don't quite work out and a few confirmed passengers have to be bumped.

If you are unlucky enough to be bumped, or 'denied boarding', to adopt the airline jargon, you will probably be entitled to compensation. A few years ago the Association of European Airlines (AEA) adopted a voluntary compensation scheme based on a 50 per cent refund of the one-way fare on the sector involved, but early in 1991 the European Community agreed new rules, which put compensation on a statutory basis. The rules lay down that passengers with a confirmed reservation who are bumped at an EC airport should receive 150 ECU (about £200) for a short- haul flight or 300 ECU (about £400) for a flight of more than 3,500 km. These amounts are halved if the passenger can get on an alternative flight within two or four hours respectively. In addition, passengers have the right to full reimbursement of their ticket for any part of their journey not undertaken, and can claim legitimate expenses.

In 1997 the EU was reviewing these rules. Consumer groups had complained that compensation should cover the whole journey - and not just the sector on which the overbooking occurs. They note that a passenger flying to the Far East via Amsterdam, who is bumped off the first leg of the journey, might be held up for only an hour or so getting out of Schiphol. But the missed connection could result in a much longer delay in getting to Asia.

Compensation for delays

Whatever the conditions of carriage may say, airlines generally take a sympathetic view if flight delays cause passengers to miss connections, particularly if the delay results in having to obtain overnight hotel accommodation. Our own experience is that most of the better-known scheduled carriers will pull out all the stops to ensure that passengers are quickly rebooked on alternative flights and they will normally pick up the tab for hotel accommodation and the cost of sending messages to advise friends or contacts of the revised arrival time.

The position is not so clear cut when it comes to charter airlines because the extent of their generosity usually depends on whatever arrangement they have with the charterer. But a number of British tour operators have devised delay protection plans that are usually included as part of the normal holiday insurance. Thomson Holidays, for instance, will normally provide meals or overnight accommodation in the event of long flight delays, and if the outbound flight is delayed for more than 12 hours, passengers have the right to cancel their holiday and receive a full refund. If they decide to continue their holiday they receive compensation up to a maximum of £60, in addition to any meals or accommodation which may have been provided. Compensation is also paid on a similar scale if the return flight is delayed.

Injury or death

Airline liability for death or injury to passengers was originally laid down by the Warsaw Convention, which was signed in 1929. The basic principal was that the infant airline industry could have been crippled if it had been forced by the courts to pay massive amounts of compensation to passengers or their relatives for death or injury in the event of an accident. The trade-off was that the airlines undertook to pay compensation up to a set ceiling irrespective of whether negligence on their part was proved. The limit was set at 250,000 French gold francs, an obsolete currency, which is nevertheless still used to this day as the official unit of compensation, and converted into local currencies.