By Gary Lee
Sunday, March 5, 2000; Page E04

Want to go from Rome to Gothenburg, Sweden, on a whim? Or hook up with friends in Vilnius, Lithuania, following a vacation in Barcelona?

Until recently, traveling from one far-flung European city to another was often a costly, time-consuming hassle. But the arrival of low-cost European air carriers and high-speed rail services has changed all that. Now it's possible to take a jet or train from just about any urban area between northern Sweden and southern Italy at relatively low cost and with far less bother.

Train travel across Europe is faster and more efficient than ever. The catalyst for the improvements was the Eurostar, the popular locomotive that breezes 25 times a day through the English Channel tunnel between London's Waterloo Station and Paris's Gare du Nord in less than three hours. In the six years since the Chunnel debuted, dozens of other high-speed routes have opened, including Eurostar service from London to Brussels in three hours, TGV journeys from Paris to Milan in less than seven hours and German rail trips from Berlin to Hannover in a swift 1 hour 40 minutes.

For those planning to spend up to a couple of months traveling between various destinations in Europe, Eurail passes are still a good way to go. Various options are available, including a youth pass allowing three weeks of travel for $499 or a Flexipass allowing 10 days of travel in first class over a two-month period for $654.

As the political and economic links between European countries become stronger, air transport links between cities all over the Continent and England have become tighter, too. British-owned Ryanair, which specializes in cheap flights out of London's Stansted airport, forged the path for cheap intra-Europe air travel.

A slew of other upstart air carriers have followed. Virgin Express offers flights out of Brussels to 10 European cities and service between Rome, Barcelona and Madrid. Buzz, the latest low-cost carrier to enter the market, is advertising round-trip flights from London to Berlin for $110. Some of the major European carriers have taken up the challenge by cutting some of their fares. British Airways is advertising round-trip flights from London to Geneva for $210.

But beating the best of the deals offered by the small carriers--such as a $140 round-trip fare from London to Prague on London-based Go--can be tough. Besides the low fares, another advantage of choosing small carriers is that they often let passengers fly one way at half the round-trip fare, allowing a return trip by train or car. Although they fly between urban airports, they get travelers close to popular countryside destinations. Italy's Air One has flights from Rome to Milan, for example, where it's a cinch to rent a car for a tour around Tuscany.

For those who need to travel between distant cities or to odd corners of the Continent, Europebyair, a group of small and mid-sized European air carriers, is worth checking out. In all, the 16 carriers provide transport to 150 European cities, ranging from Paris, Moscow and other major capitals to off-the-beaten-track cities like Tallin, Estonia, and Split, Croatia.

Europebyair requires U.S. travelers to buy flight coupons at $99 each through the company's home office in Phoenix before departure for Europe. (To buy the coupons, passengers must already have purchased a ticket from the United States to Europe on any airline.) Passengers then make reservations for intra-Europe flights either before departure or after they've arrived in Europe. A minimum of three coupons must be purchased, and one coupon must be applied to each leg of a trip. Air Greece can get you from Rome to Athens for one coupon, for example, while Spanair offers a two-legged flight from Tenerife to Barcelona that requires two coupons.

Several of the major European air carriers, including Scandinavian Airlines and British Airways, offer similar air-pass programs. Lufthansa allows passengers who already have a transatlantic ticket to buy coupons to any city in Europe that the carrier serves. The coupons cost $89 per flight segment. Like Europebyair, Lufthansa's program requires passengers to buy a minimum of three coupons.

There are disadvantages to intra-Europe air travel. For one, security at European airports can be so tight it can take a couple of hours to check in before the flight. Also, some of the new carriers are untested, raising concerns about safety. And snagging the lowest promotional fares often requires early booking.

For more information:

* EuropebyAir (1-888-387-2479, www.europebyair.com). Features travel by air pass on 16 European carriers to 150 European destinations, including such far-flung cities as Kiev and Riga.

* Ryanair (011-44-541-569-569, www.ryanair.com). Offers 34 routes from London's Stansted airport to Ireland and 15 other cities in Europe.

* Air One (011-39-06-488800, www.flyairone.it; Web site in Italian). Specializes in flights between Rome, Milan and other Italian cities.

* Virgin Express (011-44-171-744-0004, www.virgin-express.com). Offers flights from Brussels to 10 European cities and from Rome to Madrid and Barcelona.

* Go (011-44-845-605-43-21, www.go-fly.com). Features flights from London to 11 different European destinations, including such places as Naples and Rekyavik.

* Buzz (011-44-870-240-7070, www.buzzaway.com). Runs flights from London to 11 European cities, ranging from the major capitals to places like Dusseldorf and Marseilles.

* Rail Europe (1-800-438-7245, www.raileurope.com). Information central on train travel in all European countries, including the popular London-Paris Eurostar. Or try www.eurail.com, which has details about prices and restrictions of the time-honored rail pass program.