By Megan Lane
BBC News Magazine
How far can you go with £200 by plane compared with train? With budget flights costing as little as 1p, air travel is the cheapest way to get around. No wonder environmentalists worry.
It is hard to resist the lure of a bargain, and a cheap flight to exotic parts is doubly difficult to ignore. Little wonder that air travel has seen rapid growth, growth which is set to continue and undermine efforts to limit emissions of carbon dioxide.
Aviation is considered especially polluting because of the large amount of fuel used at high altitude.
This week the Tyndall Centre for Climate Change Research has warned that unless air travel is curbed, UK homes, firms and motorists will have to cut emissions to zero if the UK is to meet its pollution-cutting targets.
One option is to let the train take the strain. After all, rail is the least-polluting means of mass transportation.
UK air passengers set to rise from 180m to 475m by 2030
Target is to reduce CO2 emissions by 60% by 2050
Under current rules, aviation and shipping are not part of a country's CO2 output
Yet how far will, say, £200 get you by air compared to rail? We set out to piece together the most ambitious journeys on both means of transport, using internet booking sites.
This fantasy journey around the UK and Europe is based on ticket prices currently available for travel in four weeks' time. By air we opted for the big two in the no-frills business - a switch somewhat clunkily made by hitchhiking from Ryanair's Frankfurt base to fly from Basel with Easyjet - and by rail with the companies which connect major centres in the UK.
Our epic air journey covered more than 4,200 miles, or some 6,900 km, and cost £196.92 - enough left over for a latte and a flapjack at the airport. The cheapest flight was just 1p - plus taxes of £14.68 - the most expensive £43.37 (plus £9 tax) to travel on a Friday.
By train £200 bought just a quarter of that distance - 1,100 miles (1,770km). Even this was probably not representative of most people's experience of train travel. By booking a month in advance, unusually cheap fares were available, such as a London to Edinburgh ticket for £12.50. For details of our trip, click here.
But how can fares be so much cheaper by plane than rail?
One reason is the fact train companies pay duty on the fuel used - although the low-grade diesel that powers locomotives has lower taxes than fuels used by motorists.
Airline fuel, however, is untaxed - thanks to a series of treaties between countries. For airlines which have to buy 200,000 litres to fill a jumbo jet, this is quite a saving and in turn helps keep fares low.
The zero-tax agreement has provoked much debate recently as environmentalists have put pressure on governments for a clampdown.
Newer plane and train models produce less pollution
In turn, British Airways has launched a scheme that allows customers to off-set damaging carbon-dioxide emissions by paying a voluntary sum which is then invested in sustainable energy projects.
Airlines, however, point to other factors that make them so much more cost effective.
Unlike rail operators, airlines are not limited to a fixed track, so the skies have vastly more capacity than Britain's clogged train network. Indeed, rail operators frequently complain they can't run more trains because there is no room left on the tracks.
Low-cost airlines are also famous for trimming other operating costs, such as staff salaries, and have a fearsome reputation for finding savings at every turn. Ryanair's ban on staff charging their personal mobile phones on company premises - to save electricity costs - shows how serious cost cutting has become in the industry.
A further factor is that the headline cost of cheap flights is often augmented by additional fees - such as low baggage allowances and charges for travelling with sports equipment.
HOW WE SPENT £200 BY AIR AND BY RAIL
Ryanair Stansted-Gothenburg: £14.69
Hitchhike to Basel for Easyjet flight to Madrid: £52.37
Ryanair Pisa-Stansted: £32.11
Direct trains only
London-Lille day return: £55
Click here to return.