If you live in Bethesda or Arlington or wherever in mainland U.S.A. and you want to spend a long weekend in some picturesque spot a hundred or so miles away, it may be just as easy to jump in the car and drive there as hop on a plane and fly. Probably easier, even considering the price of gasoline.

But if you live in -- or are visiting -- the Virgin Islands, you're going to run into a lot of trouble if you try to drive the 40 miles to San Juan or further to St. Maarten or Barbados, or wherever in the Caribbean.

You could go by boat, of course, if you've got lots of time. But as a practical matter, the best way of getting from here to there is by air.

As a result, while the issue of commuter airline safety may have a universal appeal -- especially with the mushrooming air commuter industry in the wake of airline deregulation -- it is a matter of particular concern in this U.S. territory where small planes provide the only real lifeline between St. Thomas and St. Croix and other nearby islands.

Perhaps no one feels the sense of urgency more than those who head the Caribbean office of the Federal Aviation Administration. That agency has come under severe attack of late from the National Transportation Safety Board for what the NTSB has characterized as the FAA's "frequently inadequate" surveillance of commuter airlines, throughout the United States in general and in the Caribbean in particular.

The criticism stems in part from two widely publicized fatal crashes in the Virgin Islands. One, in September 1978, involved an Antilles Air Boats Grumman Goose and took the lives of three passengers and the airline's founder and president, Charles F. Blair, who was piloting the seaplane; the other, in July 1979, was the crash of a Puerto Rico International Airlines (Prinair) plane that killed the co-pilot and seven passengers.

Michael T. Fenn, the man in charge of FAA operations in the Caribbean, claims the NTSB criticism is sometimes "unwarranted" and accuses the board of taking some "cheap shots" at the FAA.

But Fenn concedes that the public criticism was one factor that led to tougher air safety regulations for commuter airlines and stricter enforcement of those regulations.

The more stringent regulations involve more frequent aircraft inspections, an improved maintenance program, more thorough pilot training and greater pilot familiarity with the aircraft and its routes.

Now, for instance, a pilot in command of a commuter aircraft must have a minimum of 1,500 hours of experience, plus an Airline Transport Pilots' certificate -- the same standard a pilot for a major carrier must meet.

This is a far cry from the previous standards, which allowed a pilot for a commuter operation to fly passengers with only 200 hours of experience and without necessarily getting an instrument rating. This is not to suggest, however, that all commuter airlines permitted pilots meeting only those minimal requirements to fly with passengers.

The message Fenn now is giving to the commuter airline operators is to follow the new regulations -- or else.

"Any operator we find making the choice of profits over safety -- as has happened before in causing accidents -- will have a long time on the ground to regret it," he told a recent gathering of commuter airline operators here.

Calling the safety record of commuter airlines across the country "unacceptable" and "in fact, pretty dismal," Fenn cited statistics showing the average airline flight is 48 minutes long compared to 41 for the smaller commuter lines, but the accident rate for the large airlines is .55 accidents per 100,000 miles compared to 3.93 accidents per 100,000 miles for the commuter airlines.

"I know all the rationalizations and ustifications and arguments on how the figures on accidents aren't comparable, and I remain unconvinced," he told the airlines people. "I hope so do you. We're comparing one apple with another, and the commuters don't look too good."

Maintaining that the new regulations will provide a safety level for commuters comparable to the large carriers, Fenn said the commuters' accident statistics will improve "only if the regulations are followed conscientiously" and declared, "The ultimate responsibility lies with the carriers."

But, he added, "I believe in the universal perfection of mankind about as much as I believe in the tooth fairy, so we (at the FAA) are taking steps to help some of the commuters along the path of righteousness."

Among the steps commuter airline operators can expect, Fenn said, are more accident prevention programs, increased pilot proficiency checks, more aircraft inspections and greater monitoring of maintenance -- in effect, a lot more people looking over a lot more shoulders.

Later, asked specifically about the performance of the two dozen small airlines serving the Virgin Islands, Fenn said that the recent safety record is "not bad, but not acceptable."

There have been two commuter airline accidents in the Virgin Islands since January 1979, and none involving major carriers.

One accident involved the Prinair plane that crashed on takeoff from St. Croix, July 24, killing eight. That plane was found to be 1,008 pounds overweight and 11 inches out of balance because of an improperly distributed load. The second crash occurred in January 1979, after an Eastern Caribbean Airways Piper Navajo with 10 people aboard took off from St. Croix and plunged into nearby shallow water offshore. No one was killed. The cause of the crash has not yet been determined by the NTSB.

Two crashes in 15 months "is not bad when you consider the number of flights in and out" of St. Thomas and St. Croix, Fenn said. "But even two is too many. One is too many. None is ideal."

Harry S. Truman Airport in St. Thomas averages about 320 take-offs and landings daily, while Alexander Hamilton Airport in St. Croix averages about 220, according to the FAA tower chiefs at those airports.

The St. Thomas-San Juan route is the busiest in the world in terms of the number of commuter passengers and commuter aircraft going back and forth. St. Thomas-St. Croix and St. Croix-San Juan are down slightly on the list but also are major commuter airline routes. Of all the U.S. commuter airlines, Prinair is No. 1 in numbers of passengers and passenger miles.

Fenn admitted that it may not be possible to meet the ideal of no crashes. However, he said, "We need to be assured that every reasonable aviation regulation has been compiled with in terms of weight, balance, a properly maintained aircraft and a pilot and crew that are properly certificated." He added: "If you've got people cutting corners, you'll have the one or two or three accidents we're trying to avoid. We want every flight to be uneventful."

Rene Gonzales, an FAA accident prevention specialist working out of San Juan, agreed with Fenn that while the FAA is "not completely satisfied with the safety record" of airlines serving the Caribbean, that record is "good," considering the number of daily landings.

While Gonzales said the FAA needs more inspectors to serve the huge commuter airline market in the region, Fenn maintained the number of inspectors now assigned here -- 11 -- "is sufficient based on a national staffing standard."

Some commuter operators themselves are on Gonzales' side of that question.

"The FAA very definitely needs more people," siad Reuben B. Wheatley, president of Aero Virgin Islands, though he added that there is "no question the FAA presence is greater now" than before.

Wheatley, whose airline was involved in 14 of the 49 official "alerts" for aircraft experiencing trouble at Truman Airport in 1979 but has never had an actual crash, said he welcomes the additional FAA surveillance.

"We were already complying with many of the new requirements before so it hasn't affected us that much, but I look at the FAA officials as high-priced, unpaid consultants that I couldn't otherwise afford," he said. "They may interfere sometimes with the operations people but, even so, I think it's helpful."

His only compaint, he added, is that because different inspectors check his operation each time, he sometimes gets different interpretations of the same regulations, "so sometimes we don't know what's expected of us."

"Generally the vast majority of commuter airlines in this area want to do what is right," said Fenn. "They are anxious to do what is right. And we are doing everything possible to make sure they understand the regulations."

The FAA is "not looking for punishment," Fenn said. "We're looking for compliance. But if we don't get compliance, we're going to put them out of business."

That will be good news to the flying public, if in fact it happens that way.

As the territory's congressional representative, Delegate Melvin H. Evans, told the commter operators at their St. Thomas forum on airline safety, the consumer has the right to expect standards as high for the commuter leg of a trip as for the part flown on a commercial carrier.

"If you have to use a commuter airline to complete your journey," Evans said, "and the safety level is not as great there as it was on the main plane and you crash, I suspect you'll be just as dead as if it happened before."