DELTA AIR LINES in April flew 4.8 billion revenue passenger miles, down from 5 billion in April 1990. Load factor declined to 60 percent from 66 percent.

For the four months, Atlanta-based Delta flew 18.4 billion RPMs, down from 18.6 billion in April 1989. Load factor fell to 58.3 percent from 62.4 percent.Delta officials said that April 1989 figures were inflated by a strike against Eastern Air Lines, which subsequently resumed flying a bigger schedule.

SOUTHWEST AIRLINES flew 820.8 million revenue passenger miles in April, up

from 736.1 million in April 1989. Load factor for April was 61.8 percent, up

from 61.1 percent in April 1989.

For the first four months of 1990, Dallas-based Southwest's RPMs totaled 3.1 billion, up from 2.9 billion a year earlier. Load factor was 60.7 percent, compared with 64.2 percent a year ago.