The National Transportation Safety Board yesterday recommended that the Federal Aviation Administration do 18 things to improve airline safety when runways are covered with ice and snow.

Safety board Chairman Jim Burnett said that, if the "reforms envisioned by the recommendations adopted today had been in effect" last winter, both the Air Florida accident here and the World Airways crash in Boston "may well have been prevented."

Most of the recommendations dealt with the Jan. 23 World Airways crash, in which a DC10 skidded off an icy runway and into Boston Harbor. Two of the 212 people on board are missing and presumed dead.

Seventy-eight people were killed Jan. 13 when Air Florida Flight 90 lifted off from a snow- and slush-covered runway at Washington National Airport and then crashed into the 14th Street Bridge.

The board has made many recommendations as a result of that accident and has emphasized improved pilot training and awareness of the problems created by snow on the wings. The board blamed the pilot, but cited circumstances that, had they been different, might have resulted in a safe flight or no flight at all.

Because of ice-blocked sensors, the Air Florida plane's engines did not produce as much power as expected. In its new recommendations, the board suggested that a government-industry task force develop a "reliable takeoff acceleration monitoring system" to would warn crews when problems such as those experienced by Flight 90 are encountered.

The board also reiterated a longstanding recommendation that markers be placed along runways so pilots can tell how much room is remaining to help them decide whether to abort a takeoff. The FAA rejected that idea once on grounds it was costly and that markers might distract pilots.

Concerning the World Airways accident, the board recommended, among other things, that the FAA require that air traffic controllers demand and disseminate information on runway braking conditions.