Holiday luggage unzipped

How big should your cabin bag be? How heavy a case are you allowed? And how much can you claim if it is lost? Welcome to the baffling world of airline baggage

On the case: checked baggage often attracts a charge (PA)

How much can I check in?

Tell me which airline, and which class, you are flying, and I will tell you how much you may check in free of charge.

Since the dawn of aviation, or at least the formation of the International Air Transport Association (IATA) in 1945, the standard allowance has been 20kg. But for the vast majority of UK passengers in 2013 it will be something different. Increasingly the allowance is nil: that applies to most low-cost airlines, plus KLM in Europe, and British Airways from Gatwick on the cheapest fares. On many charter carriers, the allowance has fallen to 15kg – usually with the option to buy an extra 5kg. Many "full-service" airlines have increased their economy allowance to 23kg: these include the big transatlantic rivals BA, Delta, United and Virgin Atlantic, as well as SAS. A few carriers are more generous: Emirates offers 30kg, while Arik Air, which flies from London to Lagos and on to Johannesburg, tops the table at 60kg, with a maximum of two bags (so to take full advantage you must take two at exactly 30kg each).

The allowance multiplies in business or first class, and for elite members of a frequent-flyer scheme; 60kg is nothing exceptional. But most airlines will decline to handle any single item over 32kg, unless you book ahead and pay.

Why do some airlines charge – and how much must I pay?

Low-cost airlines take their business model from their name. When easyJet and Ryanair began, they offered a free 20kg limit like everyone else. But on the principle that passengers should pay for the services they use, around five years ago they – and most other budget airlines – started charging for the privilege.

Ryanair has always maintained that the idea is to change passenger behaviour in order to make airport turnarounds more efficient, and therefore cut costs. It says that the majority of customers travel with cabin baggage only. But in summer, when many families are flying away on holiday, it is a real moneyspinner – typically £25 for a 15kg case for a one-way Ryanair flight. That is if you have the good sense to book in advance, online; leave it to the airport and you could pay upwards of £100.

Other airlines charge less; the starting price for 23kg on BA's European network from Gatwick is £9 each way, with longer flights at £15, so long as you book ahead. On a typical easyJet flight, the rate is £12 for one 20kg bag.

What trips up some travellers is the rule that paying for extra bags does not buy additional weight. On easyJet, for example, you can book up to eight bags (and pay typically £96 for the privilege) but they must collectively weigh no more than 20kg.

If you are on easyJet and there is any possibility that you may not travel then do not book your baggage until the night before departure. You will pay the same as if you had booked it when buying the flight. In contrast, if you pay (say) £50 for pre-booked luggage and subsequently have to cancel, you will lose the baggage fee.

How does excess baggage work?

Punitively, often. The standard rate always used to be one per cent of the first-class fare for each kilogram of weight. An extra 10kg from London to New York could cost an additional £500. Most airlines now have set rates, but they are still usually applied per kilogram and are typically £10 or £20, even for a short flight. On BA, though, you can bring a second 23kg bag in economy class on long-haul flights for just £65 (or £55 if booked ahead).

Just remind me of the rules for cabin baggage ...

Since the start of July, the number of different cabin-baggage rules is actually now higher than the number of airlines – due to the new option introduced by easyJet. Each carrier imposes its own rules on dimensions and weight, and these are drifting further apart.

The default "IATA" dimensions are 56cm x 45cm x 25cm, which means a volume of 63 litres. Top of the generosity list are BA and easyJet, which both allow these dimensions plus a laptop or handbag (BA) or a bag of duty-free (easyJet). BA has a weight limit of 23kg, while the sky's the limit on easyJet so long as you can lift your cabin bag into the overhead bin.

After that, generosity reduces. Monarch (56 litres) Flybe (51 litres) and Ryanair (44 litres) allow progressively smaller bags with a 10kg limit, with Monarch at least permitting this to be split between two bags (except at Luton, where airport rules insist on a maximum of one bag). Exceed these and you will pay a fee of £50 or more to watch your bag disappear into the hold. Charter airlines are even tougher on weight, with 5kg typical.

Virgin Atlantic allows only 46 litres and 10kg even on its longest hauls to the Far East and Australia.

Is it true that some airlines charge for cabin baggage?

Yes: Wizz Air, the leading eastern European low-cost carrier, allows one laptop-sized bag free, but anything larger costs €10 or more. In the US, Spirit Airlines has adopted the same policy.

How do I avoid losing my bag?

The easiest way: don't check it in, which could mean you switch to BA or easyJet to take advantage of their generous cabin baggage allowances. If that doesn't work for you, then try to fly direct. While baggage handling systems are capable of losing luggage even on a simple journey such as Newquay to Gatwick, far more bags go astray while in transit – particularly at hub airports. Tight connections are particularly susceptible; if your inbound flight to the hub is delayed, you may make the connection, but your bag may not.

I've arrived at my destination, but my bag hasn't. What next?

One of the more disheartening experiences in air travel is watching a baggage carousel gradually emptying with the growing realisation that your case is either still at your departure airport, or somewhere else entirely.

Report the case to the ground handler for your airline. They will ask you to fill in a PIR (Property Irregularity Report), which covers everything from a description of the bag and its contents, to your contact address. The airline has a responsibility to reunite you with your luggage. If you are staying somewhere fixed, eg a hotel or villa, it should then be a straightforward process for the bag to be delivered by courier. If, however, you are travelling onwards (eg on a cruise) it gets a lot trickier – and it may prove frustrating as they try to deliver to a moving target.

Am I entitled to expenses while I wait?

Yes, so long as you are reasonable. Don't go out and buy a whole new designer outfit – but a modest amount on T-shirts, jeans, underwear and toiletries should be fine. Some airlines will give you an allowance, while with others you may have to argue to get recompense afterwards. Your travel insurance policy may help – but I would treat it as a last resort if airline intransigence wears you down.

I haven't seen my bag for weeks since I checked it in. Who pays, and how do I get the money?

The vast majority of bags are reunited with their owners, but some never make it back – either because they are stolen or, more likely, because all visible tags are torn off and there is no way of knowing whose it is. After three weeks, the airline is liable, up to the maximum under the Montreal Convention 1999. The denomination used is the "Special Drawing Right", a virtual currency that fluctuates, but £1,100 is a rough figure.

There were some irreplaceable objects in my bag …

Which is why you should never check in anything that you can't afford to lose. No value is placed on sentimental attachment. The most useful measures you can take to avoid permanent loss: first, make your luggage distinctive, eg with a swathe of brightly coloured fabric on the handle, or simply "gaffer tape" stuck on the sides, to reduce the risk of another passenger mistakenly picking it up; next, label the inside of the bag with your name and contact details; assume that all the outside name tags will be torn off during handling.

What happens to all those unclaimed bags?

They are stored for three months by the airline that happens to have possession of it. Then they are sorted, with high-value items removed and sold separately. The bags themselves and their low-value contents are then auctioned. In the UK, the main vendor is Greasby's in Tooting, south-west London, where cases are auctioned in a kind of lucky dip, usually on Tuesdays at 10am (but check ahead on 020-8672 2972; greasbys.co.uk).

The US model is different: the town of Scottsboro Alabama is home to the lost baggage industry, with competing department stores offering saleable items reclaimed from stray suitcases. The original and greatest is the Unclaimed Baggage Center (001 256 259 1525; unclaimedbaggage.com), which has the state's largest laundry facility, washing 20,000 items a day – while technicians delete personal data from lost laptops.

Two airports turn unclaimed bags into works of art: Santiago in Chile and Calgary in Canada have created displays in the arrivals area.

Why are baggage handlers always on strike?

They aren't. As with many other groups of workers in aviation, the men and women who load and unload bags have had to cope with increased workload and reduced earnings as their employers cut rates to attract business from airlines. The ground-handling industry is extremely competitive, and the UK is ahead of the rest of Europe in having big rival companies such as Swissport and Servisair battling for business. Occasionally their union will threaten industrial action, and naturally choose peak times for the maximum effect.

What about my golf clubs/skis/bicycle?

You will probably have to pay extra, except on a few generous carriers – such as Swiss, which allows skis or snowboard and boots in addition to your 23kg baggage allowance. In any event, you will need to take it to the outsize baggage belt at the departure airport. You may additionally be asked to sign a "Limited Release", which means that if the equipment is damaged the airline will not take responsibility. It is sometimes said that outsized baggage is more likely to go astray, but before you report it as lost upon arrival, have a good look around the baggage hall for an area where odd-shapped luggage is left.

What can't I carry?

In either hold or cabin baggage, highly flammable liquids or gases, from lighter fuel to Camping Gaz.

In checked baggage, it is mostly high value stuff: money, jewels, gold, computers; essential medication or medical equipment that cannot be replaced at short notice if lost. You would also be daft to check in your house or car keys, and you won't get far if you pop your passport into the case just before it disappears down the baggage belt.

In hand baggage, avoid anything that looks like, or could be used as, a weapon. That includes the fairly obvious, such as replica or toy guns, cutlery, scissors, corkscrews, but is extended to items such cricket bats and lighters. If you need to carry hypodermic needles for medical reasons, bring a letter from the doctor explaining why.

Will the Americans break into my bag?

When you are flying from or within the US, the Transportation Security Administration (TSA) screens every bag electronically. If officers want to inspect physically the contents of your bag (for example because it contains lots of books or even cheese), they will break in– unless you use "TSA compatible" locks that can be opened by inspectors' master keys. You can buy these from specialist suppliers – or ensure there is nothing of much value in the case and elect not to lock it.

My bag has been broken into – from whom do I claim?

Possibly your travel insurance, but otherwise it is difficult to establish liability – particularly if an en-route change of plane is involved. The airline is ultimately responsible for your bag, but it goes through so many stages that it is difficult to say where a theft might have taken place. Again, the best rule is: if you can't bear to, or afford to, lose a particular item, don't check it in.

easyJet's new policy

Last week, you may have inferred from some of the headiines that Britain's biggest budget airline was cutting its cabin-baggage limit. One example: "Hand luggage reduced by more than a third for passengers on easyJet flights".

In fact, the accuracy would be improved by saying: "The cabin baggage allowance on easyJet is staying exactly the same".

All the airline has done is to offer passengers a guarantee that their bag will not be taken off at the gate and placed in the hold; if you are prepared to carry a bag of only 40 litres capacity rather than 63 litres, you will be certain to bring it on board.

But no one should be any worse off as a result of the change; it was always the case that bags may be placed in the hold, without charge, if the bins run out of space.

Measure for measure

The rule restricting travellers to 100ml quantities of liquids, aerosols or gels (LAGs) came in after the failed "liquid bomb plot" of August 2006. LAGs must be in small containers carried in a separate clear plastic, resealable bag no bigger than 20x20cm (capacity one litre). At airport security search, remove the plastic bag from hand luggage so it can be screened separately. The rule was due to end in Europe in April, but the equipment is not yet in place. The former director of security at BAA wants it eased soon – but the Department for Transport seems less keen.