The Federal Aviation Administration has drafted rules to permit new two-engine jetliners to fly lengthy remote routes that now require three- or four-engine planes.

When the rules become final, they will allow Boeing's two-engine 767 jumbo jet to be used on the most fuel-efficient North Atlantic routes, which take flights far from airports in Greenland and Iceland.

The 767 is the first two-engine jetliner to have the range for transatlantic operations, and Boeing has been pushing hard to get the rules changed to expand its sales potential.

Under current rules, a two-engine plane can be no farther from an airport than 60 minutes' flying time on one engine. Three- and four-engine planes can be no farther from an airport than two hours' flying time with one engine inoperative. The proposal by the FAA would extend that rule to properly modified two-engine jets.

Trans World Airlines, a 767 customer and the leading North Atlantic carrier, is using a modified 767 on flights between Boston and Paris with a special exemption from the FAA that permits the plane to be as far from an airport as 75 minutes' flying time with one engine inoperative.

Beginning April 28, TWA plans to use the 767 on three new nonstop routes between St. Louis and London, Paris and Frankfurt, by which time it hopes the new rules will be final.

The rules would apply everywhere, not just to transoceanic flying.

The number of engines is not the major issue, according to an FAA expert, because jet-engine reliability is so high.

The regulations concerning the number of engines required were developed in aviation's early years, when piston engines and then turboprops were common but had much lower reliability than the jets of today.

The major modifications would be to assure that a plane flying on one engine would have the same backup electrical and hydraulic systems available as a three- or four-engine plane with one engine out.

The modifications include the installation of an extra gasoline-powered generator to provide backup electricity.

Additional FAA surveillance of the airplanes and their engines also is required.