You have worked all year, criss-crossing the globe on British Airways in an effort to build up the number of BA Miles you hold in your Executive Club account. Then you start thinking about holidays and decide you want to redeem some of the thousands you have built up with free flights for yourself and your other half. The only problem is that you can’t find seats on the flights you want.

One of the big criticisms of British Airways’ Executive Club is that it is often difficult to redeem miles once you have earned them. The same criticism can be levelled at a greater or lesser extent at many frequent flyer programmes.

A spokeswoman for the airline says that there is always at least one seat for Executive Club members on every flight but the total number of seats available varies vary from route to route and from week to week depending on commercial demand. The airline says: “British Airways cannot guarantee that a member will be able to make an award booking on any specific flight regardless of the time of booking.”

The company’s annual report gives an indication of the problem. Airlines regularly measure something called revenue passenger kilometres or RPKs, the total distance travelled by fare-paying passengers. It proves a useful benchmark between airlines. British Airways also measures frequent flyer kilometres.

The annual report reveals that in the year to March 31, 2006, frequent flyer kilometres were 2.8 per cent of total RPKs. Taken at face value this would seem to imply that less than one in 30 passengers is travelling using miles. In fact, it is probably even fewer than that given that many frequent travellers will be saving towards long-haul flights.

Another key reason for finding it difficult to redeem BA Miles is that there are an awful lot of unused miles out there that have built up in the 21 years that the airline has had a loyalty programme. According to the airline’s annual report, the total number of BA Miles outstanding on March 31, 2006 was more than 127 billion. Yes, that’s right. 127 BILLION. That’s enough to go to Pluto and back (if you still wanted to go there now that it has been relegated to non-planet status) several times. A spokeswoman for the airline says: "The number of miles outstanding is not an issue. There is always a high number in issue and a lot don't ever get redeemed."

This figure includes miles awarded for flights taken on the airline but also for miles sold to partners in the programme that have not yet been used. What the figure hides is that providing a free seat on a plane has only a small incremental cost for BA. Indeed, it reckons that to cover providing free seats to people who have earned their miles on BA will cost it just £15 million. By comparison, it has made more than £350 million from selling miles to partners.

But what do business travellers think? Rachel Ashton, a regular traveller whoe works for an investment bank and a Silver member of Executive Club, told Times Online Business Travel that she managed to book a trip to Valencia for her and three friends two years ago with no problem. “I felt good knowing that I was getting all the flights for free but it used up a lot of miles and all along I kept wondering whether I shouldn’t be saving them for a more valuable trip.”

However a trip for a wedding in Sydney on miles proved impossible. “I rang up three months in advance and asked for a ticket to Sydney. The person on the other end of the phone just laughed and said that people often booked tickets on popular routes as soon as they became available.”

British Airways says that awards flights are made available 355 days before the departure date of a flight. If you know you want to go to a particular destination on a particular date and have plenty of advance notice – something that few people have in reality – then you might just be in luck.

Despite that hiccup, Ashton says she has taken out a British Airways American Express card to boost her miles-earning potential. The card comes in two varieties. A free of charge classic card gives you 3,000 miles on acceptance, two miles per pound spent in the first three months and one mile per pound thereafter. If you spend £20,000 in any year, you get a free companion ticket. The Premium Plus card has a £120 annual fee, offers 6,000 miles on acceptance, two miles per pound spent in the first three months and 1.5 miles per pound thereafter. You also earn double points on BA tickets bought on the card and a companion ticket if you spend more than £10,000 in any one year.

Ravindra Bhagwanani of Toulouse-based Global Flight, an expert on frequent flyer programmes, says: “I like Executive Club. It is fair and robust but it does not target everybody, just the business traveller in Club World or First. If you are a economy passenger you might be better off in another programme. Also it does not have a very larger partner network so it’s harder to earn miles that way. As a result, it is very difficult to get miles within a short time.”

He is somewhat dismissive of the BA credit card. “You need to look at what it is really worth to you.”

Even Ashton feels uncertain about the card. “I ended up putting everything on it for a year to get a companion ticket but because not everywhere takes American Express, I ended up paying more for some things than if I had paid with another card.”

For many people, including Ashton, the appeal of being in Executive Club is not so much the promise of ‘free’ flights (plus taxes and charges à la Ryanair) but the lounge access that you get if you are a Silver or Gold member. Ashton said: “I would often prefer to pay £50 more for a BA flight than one with easyJet or Ryanair just because I know I’ll be able to get into the lounge with my card.”

Ashton now has 161,000 miles in her Executive Club account, enough for a two returns, one to Sydney and another to Venezuela. "I always think I'm going to use them for something really special but I'll probably end up using them flying to Scotland or on upgrades," she says. "But I'll admit it; they have me hooked."

What are your experiences of BA's Executive Club? Have you found it difficult to redeem your miles? Are you hooked on miles? Let us know using the form below.