Long-haul discount airlines
At the opposite extreme from the business-only airlines are the long-haul discounters. Much like Southwest and JetBlue in the U.S. and Ryanair and easyJet in Europe, a number of airlines have emerged to provide "discount" service on transatlantic routes. As with other discounters, low fares may translate to fewer amenities.

Who: There are a number of transatlantic discounters, including Eurofly, Zoom, LTU, Condor, Martinair and Fly Thomas Cook.

Cities served: Because several of the transatlantic discounters (particularly Condor, Martinair and Fly Thomas Cook) have a mainly European clientele, they tend to fly into and out of only a few popular American vacation cities, such as Miami, Orlando and Las Vegas.

Meanwhile, Eurofly flies from New York's JFK Airport to a number of cities in Italy. Zoom serves London (Gatwick) from Fort Lauderdale, JFK and San Diego. And LTU offers the greatest number of choices, flying from a wide range of U.S. gateways to a variety of European destinations (with an emphasis on German cities).

Cost: Despite the "discounter" moniker, we found fares on these airlines to be pretty similar to the economy-class offerings on traditional airlines — close enough that it's worth checking both. For example, LTU's $672 fare for a round-trip New York - Munich flight was quite a bit higher than the United flight we found for $457 on the same dates — but Zoom won big with a $625 round-trip flight from New York to London during the summer high season; the next runner-up was $970 on Air France. (All prices include taxes and fees.)

Pros
The competitive pricing could save you money over economy-class fares on the major airlines.

If you're flying to a country where the discounter is based (such as Italy for Eurofly or LTU for Germany), you could find a nonstop flight that's more convenient than a similarly priced connecting itinerary on a major airline.

Cons
Many flights may be seasonal or may not depart every day of the week.

Many of the discounters do not offer frequent flier programs, and their baggage limitations may be a bit stingier than those of the traditional airlines.

The discounters do not serve as wide a variety of cities (in Europe or the U.S.) as the traditional airlines.

Premium economy class
If you can't afford business class but are tired of the cramped conditions in coach, here's your middle ground: a number of traditional airlines are letting passengers pay a little extra for a better experience in economy. Perks generally include expedited check-in and boarding, greater seat pitch and an extra in-cabin amenity or two (such as complimentary headphones). You won't get lie-flat seats or meals served on fine china, but a little extra legroom can make a big difference on a long flight.

Who: Virgin Atlantic, United, Scandinavian Airlines, BMI, British Airways and Air New Zealand (only on certain routes).

Cities served: Virgin Atlantic, BMI and Air New Zealand fly to the British Isles from a number of U.S. gateways, while the other airlines serve a wider range of European cities.

Cost: Premium economy fares are significantly lower than first or business class fares on the same airline and typically cost less than the offerings from the all-business airlines as well. However, a round-trip premium economy fare will usually set you back double the cost of a basic round-trip economy fare (or more).

On an upcoming Virgin Atlantic flight from Newark to London (Heathrow), we found a premium economy fare of $1,348 round-trip (with taxes and fees), as opposed to $596 for the same flight in regular economy class. Meanwhile, Scandinavian Airlines quoted us a fare of $1861.43 for premium economy service between Newark and Stockholm, as compared to $811 in economy.

United handles its premium economy class a bit differently than most other carriers. Its Economy Plus seats (which offer five more inches of seat pitch in the front of the coach cabin but seemingly no other real perks) are given out on a first-come, first-served basis to high-ranking frequent fliers and to travelers who pay the $349 annual fee for Economy Plus Access. If there are any seats left over before the plane departs, ordinary travelers may be able to upgrade to an Economy Plus seat for $25 to $30 one way.

Pros
Premium economy is ideal for leisure travelers who want an option between economy and business class in terms of price, comfort and perks.

Because premium economy is offered by many major airlines, travelers have far more itinerary and schedule options than they do on the all-business airlines or the transatlantic discounters.

Cons
While premium economy is cheaper than business class, it still runs more than twice the price of a regular economy ticket and may be unaffordable for travelers on a budget.

The perks of premium economy class vary widely by airline, and may not amount to much beyond a slightly wider seat. Be sure to read up on what's included before ponying up the extra money.

Premium economy is mostly available on foreign carriers; the one U.S. airline that offers it (United) charges a lofty annual fee.

Don't miss these Travel stories from msnbc.com   Slide show: Capitol Visitor Center open at last   Plane lands with shattered windshield |     Video   Travel pinched by global financial crisis Good to go: Travel gifts for tight budgets 9 ways to tell if your travel pro is crooked

MORE FROM TRAVEL

Travel Section Front

Good to go: Travel gifts for tight budgets Miami hotel gets $1 billion makeover Chocolate lover’s paradises around the world Images: Floods in Venice The unfriendly skies: Best and worst of air travel No Who-ville in Louisville this Christmas Your turn! Travel to the Ends of the Earth 6 easy kid-free getaways Honoring tradition in troubled times Don't go here! 24 sights not to see Travel Section Front   Add Travel headlines to your news reader: