ON NON-SMOKING trains and buses, and in the backs of non-smoking taxis, militants among the United States' 57 million smokers will suffer on their way to Washington, DC, on 25 September for a Smokers' Rights March past the non-smoking White House.

However, a few hundred of the thousands expected at the rally will already be on cloud nine, having puffed their way to Washington at 30,000ft on America's most radical airline, set up solely for smokers and launched just in time for the event.

Circumventing the law in a country where all domestic flights less than five hours are smoke-free, the Smokers Express airline has been established by two Florida smokers as a members-only club, freeing it from federal legislation; and 5,000 people from 18 countries - a third of them non-smokers - paid dollars 25 a head to join the club before its founders had even bought their first plane.

'Our membership is very diverse, including 66 per cent women,' said Mickey Richardson, a Florida publisher who teamed up with William Walts, a property developer, to fill a vacuum left when the smoking ban was introduced in 1990. 'For too long smokers have been pushed to the back of the bus.'

Smokers Express will use a small fleet of specially converted DC-9 aircraft on routes from its home base of Orlando to Las Vegas, Dallas, Miami and other East Coast destinations. There are no plans for international flights, save to the Caribbean.

The reconditioned short-haul planes have been chosen for their efficient air-conditioning system, which changes cabin air every three minutes, compared with every six to 15 on other airliners. 'We will also change the system's filters every week, not every six months,' said Mr Richardson.

With more than 100 smokers pursuing their habit at any one time in the confines of an aeroplane with a three- hour range, the efficiency of the air cleaning is a top priority, he said. 'The air on my planes will be cleaner than on non-smoking planes.'

The airline will differ from others in less subtle ways, including burger and steak meals and a free lotto ticket for each passenger (who must be over 21). 'We will offer free cigarettes as a matter of course,' Mr Richardson added.

To the envy of established airlines struggling to break even, Smokers Express expects to be profitable from day one, but its success may be short- lived. The trend towards no smoking on airliners is close to becoming international law. The International Civil Aviation Organisation (Icao), a United Nations affiliate with 174 member nations, is pushing for a worldwide smoking ban on commercial flights within three years.

The Icao has said that it 'urges all contracting states to take necessary measures as soon as possible to restrict smoking on all international passenger flights with the objective of implementing complete smoking bans by 1 July 1996'.

To counteract the withdrawal symptoms that smokers might suffer on long flights, the Icao suggests that airlines provide 'nicotine chewing gum, sprays and dermal patches'.

The call for a ban, supported by President Bill Clinton, follows medical research by bodies including the World Health Organisation which claims that smoking not only presents a safety risk in aircraft but also can have adverse physiological effects on cockpit and cabin crews. ('We used to draw lots to get out of doing the smoking section,' says a former stewardess in Canada.)

The potential health hazard of a smoke-filled plane is not something that bothers Patrick Cox, a Surrey accountant, who watched a publicity photo session for the airline in Orlando during a recent holiday. 'I think it's a marvellous idea,' he said. 'There's a real comradeship (among smokers). Non-smokers treat us like pariahs. It's then that I deliberately chain smoke.'

Airlines are gradually moving towards complete non-smoking flights, regardless of legislation. In response to passenger pressure, British Airways will next month introduce a no-smoking policy on European flights of less than 90 minutes and selected intercontinental flights to California and Hong Kong.

'Passengers are the ones giving us the steer on this,' said a spokeswoman for BA.

A blanket ban is something that most airlines would like to avoid. Smokers Express claims that 12 per cent of smokers stopped flying after the ban on US domestic flights. Yet Air Canada, whose worldwide network has been smoke-free since October 1990, noticed only a temporary fall-off in passengers on some European flights.

But the founders of Smokers Express will be hoping that the millions of smokers unable to travel as they wish will turn a rebellion into a money-spinner.

Smoke-free flying: Smoking is banned by law on domestic flights in Australia, Canada, Denmark, France, Nigeria, Norway, Saudi Arabia, Sweden, Thailand and the United States (except some flights to Hawaii and Alaska), and on international flights on Canadian- registered aircraft.

Aer Lingus bans smoking on domestic flights and between Ireland and Britain. Air France bans it on flights between many European countries. Air UK bans all smoking; BA bans it on domestic routes and, from next month, on European flights of 90 minutes or less. Virgin Atlantic bans smoking in Upper Class on selected flights to Florida. British Midland scheduled services are totally non-smoking. SAS bans smoking on all flights within Nordic countries.

Cathay Pacific operates no-smoking flights from Hong Kong to London and other destinations. Singapore Airlines' flights to and from Heathrow are non-smoking from next week.