The Washington metropolitan area is so blessed with low-fare airlines, we don't have to fly them to reap the benefits.

Thanks to major airlines' tendency to meet the fares of low-fare carriers on competing routes, ticket prices from Washington to dozens of destinations served by Southwest, Frontier, Pro Air, Sun Country and other low-fare lines are significantly lower than they would be otherwise. U.S. Department of Transportation research shows that when low-fare leader Southwest Airlines begins servicing a route, for instance, total traffic to that market increases two or three times, while fares for all carriers serving it drop 50 to 66 percent. Effects are similar, if not as dramatic, for smaller discount carriers.

In other words, you don't have to fly AirTran to Atlanta to get its $128 round-trip fare. Delta flies there, too, for the same price. So if you play your cards right, you can fly a major carrier at low-fare airline prices.

But--and you knew a but was coming--playing your cards right is not always possible, meaning it is often either necessary or easier to fly with the discounters. For one thing, major carriers sometimes limit the seats available at the low price, preferring to sell as much of their inventory as possible at higher prices to business travelers and other price-insensitive customers. And the majors often attach the all-too-familiar litany of leisure-travel restrictions to most low-priced seats: 21-day advance purchase, a Saturday-night stay and travel at non-peak days and times.

The low-fare lines, by contrast, usually make most (or even all) seats available at the lower price, and most don't require as much (or any) advance purchase, Saturday sleepovers or even round trips. Depending on your particular travel needs, you may save hundreds of dollars by choosing the low-fare airline, despite the majors' claim of a comparable price. A few for-instances (fares may have changed; we cite them here for comparison purposes only):

* Low-fare carriers Southwest and MetroJet fly round trips from BWI to Chicago, nonstop, seven-day advance purchase, for $148. American and United quoted prices between $315 and $322 for the same route and requirements.

* AirTran charges $408 for an advance-purchase Dulles-Atlanta business-class round trip; Delta asks $1,206 for a first-class seat on the same route. (Delta doesn't claim to compete with AirTran's business-class price, but it's doubtful that the extra pampering you get in Delta's first class is worth $798).

* Southwest will get you to Cleveland and back--nonstop, 14-day advance--for $66. That's $12 less than the majors charge for the same route and restrictions--hardly a deal worth chasing, and more an illustration of the way majors and discounters play a constant game of one-downmanship to wave the low-fare flag.

So in the cases where fares are similar, why would you not choose to fly the low-fare folks? By all objective measures available, safety is not an issue. Despite the spectacular tragedy of the 1996 crash of a ValuJet (AirTran's corporate forebear) aircraft into the Florida Everglades, killing all 110 people on board, no hard data or industry consensus suggests low-fare carriers are less safe than the majors. None of the industry analysts or insiders interviewed for this story suggested any of the carriers listed in our accompanying chart (see Page E9) was unsafe. All airlines, whether majors or low-fare, must comply with the same Federal Aviation Administration safety standards and procedures (and, following the ValuJet disaster, the FAA revised its procedures for certifying new entrants and for monitoring the outsourcing of maintenance to outside contractors).

As for the data, they are not much help, for the happy reason that crashes that result in fatalities are so rare and widely scattered among all passenger lines that there are no statistically significant patterns. Depending on which group of years you choose to study, the data can be used either to condemn or exonerate low-fare carriers.

Using government and private data gathered by airline safety analyst and aircraft engineer Todd Curtis, who runs the AirSafe.com Web site, from 1996 to 1998 the seven low-fare airlines serving our region logged about 2.5 million takeoffs, with one fatal accident--the ValuJet crash. During that same period, the U.S. majors flew more than 25 million legs with seven fatal accidents. Do the math, and majors suffer a fatal crash every 3.5 million takeoffs, the low-fares one every 2.5 million. But shift the dates by a single year (eliminating 1996 and the ValuJet crash) and the low-fare crowd appears infinitely safer. In other words, the numbers can't tell us anything useful here. Any fears that small, low-fare carriers are unsafe are based on something other than fatality or crash statistics.

So, if safety's a non-issue, what's left? Aside from the very minor "sacrifices" of giving up airline meals and (perhaps) assigned seating, there are two potentially substantial trade-offs to flying low: the lack of a rich, full-bodied frequent-flier program, and difficulties related to some budget carriers' smaller fleets and route structures.

Let's start with the reward issue. Many people try to plan their flights to maximize the miles they can accumulate in a major carrier's frequent-flier program. Even fly-once-a-year-to-see-the-folks-and-once-a-year-to-Vegas types can play the frequent-flier game by patronizing big airline partners like hotels, restaurants, credit card firms, long-distance telephone companies and many other businesses that don't require you to leave the ground. Fliers more frequent than that often stick with big airline plans to pursue the class upgrades, bonus miles, lounge access and other droolsome perks of the airborne plutocracy rather than seeking lowest fares.

While most bargain carriers maintain some form of loyalty program, few pay off as richly as the majors' do. In some low-fare carriers' plans, you can redeem miles only for flights on the carrier's limited route system--essentially meaning your reward for loyalty is a modest discount off your fares, say one free flight for every 12 you pay for. Nice, but not the two-tickets-to-Hawaii-or-okay-then-Paris that many frequent fliers crave. Some low-fare lines have no loyalty plans at all. MetroJet, the low-fare spinoff of US Airways, and Delta Express, spawn of Delta, tie into their parent firms' full plans and Southwest's big route structure lets even the monthly BWI-to-Manchester flier enjoy rewards to a wide variety of U.S. destinations, including holiday favorites Florida and California. For details on the perks of frequent flight with the low-fare lines, see our chart.

The Achilles' heel of the sector may be that many players fly with precious few aircraft, and thus offer low frequency of flights from our area (again, the chart provides details). Pro Air, for example, operates with only four planes, which contributes to its limited D.C. area service (three daily flights between BWI and Detroit). A small fleet also subjects customers to difficulties in the case of equipment failures. If one of United's planes at Dulles goes out of service, the airline has enough planes and mechanics around to keep disruption to a minimum. Not so with Sun Country, say, which flies 16 planes and operates just one flight a day out of Dulles. For Sun Country, one lame plane puts about 6 percent of its fleet on the sidelines (though the carrier expects its fleet to grow to 22 planes in January).

"For leisure travelers, it's not so life threatening" to sit through a delay, says Randy Petersen, publisher of InsideFlyer magazine. "But if you're closing on an IPO or doing due diligence, you're going to fly a major." Almost every budget airline is embarrassed by these problems at some point, particularly during its start-up phase. This shoestring phase is one reason observers give to explain why many low-fare carriers fail within their first few years.

"If you have only one daily flight [on a route] you have nothing--nothing--to offer" customers in the event of a cancellation or mechanical problem, says Daryl Jenkins of George Washington University's Aviation Institute. When he must be somewhere on a tight schedule, Jenkins looks for carriers with "at least three or four daily flights, with the last one being a lot later than 5 p.m." to help avoid unplanned overnighting if he misses an afternoon flight.

Aside from Southwest (which has plenty of planes and routes, even compared with the majors), most low-fare firms have agreements with other carriers that can help move displaced passengers when flights are canceled. Best protected from cancellation and delay debacles are Delta Express and MetroJet, which can tap into the resources of the mother ship in times of need.

But even on carriers without wealthy parents or interline deals, the worst-case scenarios rarely play out, says David Ulmer, executive vice president of Roberts Roach & Associates, a Hayward, Calif., transportation and management consulting firm. "Your flight will fly 98 to 99 percent of the time, just like the big guys," he points out. And he notes that low-fare carriers don't overbook their flights as often as majors do, so you're less likely to get bumped.

Predictably, every low-fare airline we canvassed claimed to offer quality customer service--in fact, most trumpeted their "people skills" when asked what distinguished them from their competitors (although a Delta Express spokeswoman came clean with the admission that "we don't offer the same level of service as Delta Air Lines." Pressed for elaboration, she softly back-pedaled, saying, "The main difference is the food; Delta has meals and we just offer snacks.").

Among industry analysts and experts, Southwest and Frontier won high marks for customer service. A study published in the June issue of Consumer Reports Travel Letter gave AirTran and Southwest high marks for customer service compared with the majors, but it didn't evaluate other low-fare lines serving our region. Consumer Reports did conclude that, overall, the service on low-fare airlines is about equal to that of major carriers. Based on complaint letters received by the DOT, Southwest, the oft-imitated and so far unequaled king of low-fare success, has ranked first in customer satisfaction among the 10 largest U.S. lines for the past eight years and in on-time percentage for the past seven years. Southwest also ranked first in baggage handling from 1992 to 1997. Alas, DOT's studies didn't include other discounters.

Finally, setting aside all the rational, self-interested reasons to choose or avoid low-fare carriers, there's the grand philosophical motivation, the appeal to the common good. That is, we need to support low-fare carriers because they are the most potent force driving fares closer to affordability. If major carriers meet low-fare airlines' prices--and we all choose to fly the majors for reasons of perks, loyalty or habit--the low-cost lines will eventually go away, killed by the public's reluctance to support the very force that holds fares down.

And--don't kid yourself for a minute--if the low-fare carriers go away, so will the low fares.

John Briley covers the airline industry for the Travel section.