It's 9 at night. My ear is sore from Air Florida's busy signals, and I'm close to bellowing, "I'm mad and I'm not going to take it anymore!"

The trouble is, I can't quit. I have a sentimental attachment to flying at the lowest possible fare, and Air Florida is high on the roster of feisty airlines, the lengthening list of "low-fare" carriers emerging on metamorphosing in the wake of airline deregulation to challenge the biggies.

Suddenly, to and from Florida and various Carribean destinations, the one-time intrastate airline is making waves, doing its best to undersell everyone and frequently succeeding. Air Florida has just taken another step and introduced a Miami-London route with fares that -- so far, at least -- even undercut those of Laker, one of the early low-fare mavericks.

My own interest in traveling with Air Florida is double-barreled. Like many of the new low-fare leaders, the airline not only slices prices, it removes restrictions. I can buy a cheap seat without paying up three or four weeks ahead, I can switch flights, I can stay as long as I like, and on international flights I can have free stopovers at any intermediate spot I choose. I also know that all the line's seats, not just a limited number of them, go for the advertised "lowball" prices.

Not all of the other new or newly "different" cost-cutter airlines offer precisely the same possibilities. But they're worth noting -- and worth checking even when they don't fly to your front door. That's because at times it's also economical to fly part way with one airline and the rest of the way with another. When you're out stalking the elusive bargain buy, then, remember these names: Southwest, Pacific Southwest, Midway, Capitol International, World, Trans America, New York Air and Empire (see details in summary at the end of this story).

I intend, too, so to keep an eye out for some newcomers, airlines not yet in the air. Reportedly planning low-fare services starting "soon" are People Express, Muse Airlines, Wings International, Jet America, Air International.

So how can they do what bigger lines say they can't do, namely keep prices down and passenger loads up? Not easily. They all claim, though, to have become expert in the art of lowering overheads. In some instances, that means being non-union, a fact that's prompted the strong Air Line Pilots Association to put together a $5 million war chest to try to instigate a change. (ALPA's view is that "unionized airlines are safer airlines. The new airlines coming onto the market fly by minimum requirements." But since all airlines fly under FAA rules, ALPA doesn't make any "unsafe" charges.)

Low-fare operators also generally adopt one or more techniques such as: operating fule-efficient aircraft (many use 737s and DC-9s, though Empire, still basically a commuter line, uses both 85-passenger Fokker jets and 19-passenger Metro-IIs); scrapping meal services and putting seats in what would have been galley space; instituting one-class service with discounts only for flying off-peak; dropping destinations during periods when there's no demand.

Southwest, which is fast becoming the role model to watch, does what's called supermarket ticketing; your ticket doesn't have your name on it and if you lose it, there's no refund. You can also buy a "book" of tickets at a special rate, and a "net fare" arrangement means travel agents can buy Southwest tickets at wholesale and sell them for whatever markup they choose. (Travel agents in some cases have declined to sell Southwest tickets, however, because they don't like the system.)

What you can't do is "interline," that is, have Southwest ticket you for other airlines' flights and transfer your baggage automatically. They don't have joint fares with any other carriers, either. Rules for flying with low-fare carriers, therefore, include asking a lot of questions about amenities and operating procedures.

Some airlines and travel agents are still debating whether the airline deregulation bill passed by Congress in October 1978, will prove in the long run to be a good or bad thing. But the fact is that, thanks in part to the trend toward low-fare, high-frequency airlines, price competition has begun to heat up and occasionally boil over with benefits for the ticket-buyer.

Item: Before deregulation, Pacific Southwest was a California-only low-fare airline. But its entrance into the Los Angeles-Salt Lake City market caused a rollback of prices there. At present, the airlines notes, PSA's $90 one-way fare is matched by Western, which in 1979 was charging $109.

Item: Fares between New York and Chicago are still moving up, and are now about $278 for a round-trip excursion, $184 one way. Midway Airlines, though, offers unrestricted fares of $87 each way off-peak, $122 in prime time, and a few other carriers have scaled down, or are preparing to scale down, rates on at least some seats.

Item: The president of Southwest Airlines graphically describes his carrier's way of operating by saying "we are the largest bus line in Texas," and proves is with unrestricted one-way fares of $25 after 7 p.m. and on Saturdays between five-city pairs, including houston-New Orleans.

What this means, of course, is that "all air fares are exactly the same" has gone the way of "no nice girls kiss on the first date." By the same token, it doesn't mean that the cost-cutter airlines, once out in front, necessarily stay in front.

Trans America, for instance, espouses the low-fare philosophy, but on its New York-Amsterdam service, it only claims to be "among the lowest," not "the lowest."

And New York Air's bold bid to grab a big share of the Washington-New York-Boston market by undercutting Eastern's shuttle price hasn't gone unchallenged either. Eastern has lowered its New York-Boston rate to $49 and charges $59 New York-Washington, both fares $10 higher than New York Air's peak-time rates. New York Air, however, charges $29 on all weekend flights and on two daily off-peak flights. New York Air also began Washington-Boston service with a $69 fare. Other airlines on that route have dropped their $108 fare to $69 on a limited number of seats. Pan Am and World have put in some competitive fares as well: Pan Am has a $29 Newark-Washington flight and World has a $27 Newark-Boston standby fare.

So there I was, finally flying Air Florida. Seat price was adequate, meal service "no frills." On domestic flights, there's snack service only. During flights that bridge meal hours, that means beverages and a sandwich with a piece of fruit or a candy bar; otherwise, it's beverages and a package of nuts. Nothing else is out of the ordinary, unless you draw the flight attendants and check-in clerks that I did. Most of them seemed more harassed and captious than hospitable and cordial.

Never mind. If all the cheap-seat, low-fare airlines turn out to be this good, I'm not going to throw so much as a pebble.

(And don't write off the major airlines. Several have begun slashing regular fares and offering limited-time promotional fares in hope of boosting laggins sales before the summer season begins. Now, more than ever, high-flying bargain hunters must shop around.) Where the Little Ones Fly

Here are the areas served by some of th better-known cost-cutter airlines; dial (800) 555-1212 to find out if the airline you want has a toll-free phone number, or consult local directory):

Southwest: Goes to 14 cities in Texas, Louisiana, Oklahoma, New Mexico.

Pacific Southwest: Intra-California around Los Angeles, San Francisco, San Diego, Burbank, Oakland, Sacramento, San Jose; "outside" to Salt Lake City, Phoenix, Las Vegas and -- soon -- Reno.

Midway: Fans out from Chicago to New York, Detroit, Cleveland, Kansas City, St. Louis, Omaha and Washington, D.C.

Capitol: Flies New York to Los Angeles, Brussels, Frankfurt, San Juan. In April, will add New York to Boston and Chicago, Boston to Brussels, Chicago to Los Angeles.

Trans america: Flies New York to Shannon and Amsterdam; starting end of May, will add Los Angeles-Shannon-Amsterdam.

New York Air: Offers high-frequency flights from New York to Washington and Boston, and between Washington and Boston, and New York and Cleveland.

Empire: Covers Rochester, Syracuse, Utica-Rome, Ithaca, White Plains, New York-Newark, Boston, Hartford, Washington, Montreal.

Air Florida: Flies from Miami to New York, Washington, Houston, Dallas, Amsterdam, Brussels and various Caribbean and Central America points.

World: Transcontinental Newark-New York, Baltimore-Washington, Boston to San Francisco-Oakland and Los Angeles, plus Honolulu; (beginning in May), London and Frankfurt.

The following airlines are not yet in the air.

Peoples Express: Plans to fly New York-Newark to 27 cities in East, South and Midwest, starting in May to Columbus, Norfolk, Buffalo.

Muse Airlines: Has filed to serve 24 cities, mainly in Texas and the Midwest.

Wings International: Hopes to get off ground in September with a low-priced first-class-only service between New York and Los Angeles.

Jet America: Planning initially for service between Long Beach, Calif., and Chicago.

Air International: Will aim at cities in New York, Pennsylvania, Ohio, Indiana and Illinois, plus Denver, Little Rock, Memphis, Oklahoma City, Tampa.