Are you planning a European tour, stopping in multiple countries? If so, did you know that aside from car rentals and trains there is a third option for getting around? Europe is home to a variety of budget airlines who offer inexpensive plane fares that make traveling by air far more accessible than you may think. 'Inexpensive' means as low as $155 from Frankfurt to Venice (Ryanair), or $63 from Bilbao to London (easyJet), or even $115 from London to Amsterdam, back to London again (easyJet). 

Many of these airlines offer online reservations, allowing you to research and book your entire trip before ever leaving your home.  As always, allow yourself plenty of time to make arrangements, and shop around for the best rates.  If there isn't a direct flight to the city you wish to visit, consider flying in somewhere very close to it.  Following is an 'insider's guide' to the largest, low-cost European airlines by volume:

• Ryanair:  ryanair.com Irish, 346 routes/21 countries.
• easyJet:  easyJet.com English, 267 routes/21 countries.
• Air Berlin: airberlin.com German, 356 routes/14 countries
• flybe: flybe.com English, 99 routes/6 countries
• Germanwings: germanwings.com German 98 routes/21 countries
• Hapag-Lloyd Express: hlx.com German, 83 routes/11 countries
• Norwegian Air Shuttle: norwegian.no Norwegian, 77 routes/21 countries
• Thomsonfly: thomsonfly.com English, 73 routes/9 countries
• Sterling:  sterlingticket.com Danish, 71 routes/9 countries
• Sky Europe: skyeurope.com Slovakian, 70 routes/19 countries
• Wizz Air:  wizzair.com  Central European, 60 routes/18 countries

Sample one-way comparison itineraries (based on bookings one month in advance):

London to Paris
Plane: easyJet, $76, 1 hour 15 minutes
Train: RailEurope.com, $150, 2 hours 50 minutes
Automobile: Not possible.  (One-way rentals are not allowed out of the UK, according to autoeurope.com and Hertx)

Venice to Rome
Plane: Ryanair, $27, 1 hour 5 minutes
Train: raileurope.com, $58, 4 hours 33 minutes
Automobile: autoeurope.co, $127.66 (plus gas), about 5 hours