The nation's big oil companies continued to turn in impressive earnings reports. Exxon Corp., Texaco Inc. and Gulf Oil Corp. announced big jumps in profits and sales for the fourth quarter yesterday, and Union Oil Of California posted an increase and Cities Service flat results Wednesday for their fourth quarters.

But while the other companies also reported increases in annual figures, Texaco and Cities Service said earnings had fallen in 1978.

And General lectric Co.'s centennial year produced the highest sales and earnings in the history of the nation's largest producer of electrical equipment, the company said yesteday.

The oil companies pointed to better results in currency transactions and the high demand for gasoline in the United States as reasons for the large fourth-quarter increases.

Oil analyst Eugene Nowak at Blythe Eastman Dillon said the firms also benefitted from the supply problems growing out of the volatile political situation in Iran in the last few weeks of the quarter. "As long as Iran is shut down, yor're going to have a very tight supply, and that's a very good element in any industry," he said. Exxon, the nation's largest oil company and second-largest industrial firm, said its profits rose 49.2 percent in the fourth quarter to $850 million ($1.91 a share) from $573 million ($1.28) a year ago. Sales rose from $15.53 billion to $18.06 billion the firm said.

For the year. Exxon said earnings were $2.76 billion ($6.19), up from $2.44 billion ($5.45) in 1977. Sales rose from $58.46 billion to $64.46 billion.

Texaco, No. 3 in the industry, said fourth-quarter earnings were $328.3 million ($1.21 a share) compared with $190.9 million 70 cents) in 1977. Sales rose from $7.2 billion to $8.27 billion.

Texaco attributed its fourth-quarter profit rise to better dollar-exachange rates but heavy losses in the first half of the year because of the dollar's slide dragged down its annual dollar's slide dragged down its annual profits. For the year, Texaco said profits were up to $852.5 million ($3.14) from $889.99 million ($3.28) as sales rose to $29.13 billion from $28.44 billion.

Gulf, ranked fifth in the industry, said its earnings rose to $253 million ($1.30) a share, in the fourth quarter from $175 million (90 cents) a year ago. Sales rose to $5.45 billion from $5.10 billion.

Annual earnings went up to $791 million ($4.06) from $752 million ($3.86) in $977. Revenues were $20.09 billion compared with $19.81 billion in 1977.

Union Oil of Los Angeles, the 14th largest oil company, said a gain from the sale of its one-third ownership in a Japanese oil company helped boost its fourth-quarter profits by 52 percent from a year earlier. Net income in the period was $123.7 miooion ($2.81 a share) against $81.1 million ($1.79) in the final quarter of 1977. The company did not report its revenue.

For the full year, Union Oil had income of $382.3 million ($8.64) on revnue of $6.5 billion compared with 1977 earnings of $334.2 million ($7.39) on $6.1 billion in revenues.

Cities Service, ranked No. 17, had fourth-quarter earnings of $54.2 million ($1.96) a share) against $54.3 million ($1.96) in the comparison period. For the year, Cities Service reported $202.5 million ($7.32) in earnings on revenue of $4.712 billion. In 1977, earnings were $210.2 million ($7.62) on revenues of $4.436 billion.

Earnings for 1978 were $1.23 billion ($5.39 a share), up 13 percent from the $1.088 billion ($4979) earned a year ago. Sales for the year were $19.65 billon, a 12 percent increase from the $17.52 billion in 1977.

Fourth-quarter earnings also were up. Net income was $364 million ($1.59) compared with $332.4 million ( $146) a year earlier. Sales in the quarter were $5.4 billion, up from $472 billion.

Several of the nation's airlines reported big gains in annual earnings yesterday, benefitting from the travel boom that set industry traffic records for most of the year.

But the discount fares which touched off that boom took their toll in the final quarter of the year, when a slowdown in traffic produced poor results for the carriers.

UAL Inc., parent company of United Airlines, the nation's largest, said annual earnings more than doubled from $135.1 million ($5.41 a share) to $302.3 million ($11.93). Revenues were $3.89 billion, up form $3.27 billion.

Ual/ noted that the earnings figures included $139.6 million ($5.52) of investment tax credits.

But the airline's fourth-quarter picture was not quite so rosy. Net income fell to $16.5 million (63 cents) from $44.2 million ($1.77) a year ago.

Continental Airlines an Western Airlines, which are working on a merger arrangement announced last fall, both reported fourth-quarter losses despite increases for the year.

Continental said it lost $314,400 in the fourth quarter compared with a $5 million (35-cent-a-share) gain in 1977's fourth quarter. Sales in the quarter increased to $205.2 million from $173 million.

For the year, however, Continental said it made $49.2 million ($3.29), up from $25.6 million ($1.77). Revenues increased to $774.7 million from $651.1 million in 1977.

Western lost $3.1 million in the fourth quarter compared with a gain of $1.4 million (7 cents a share) in 1977's fourth quarter. Revenues grew, however, from $173 million to 199.4 million.

Western's annual figures showed an earnings gain from $12.7 million (96 cents) in 1977 to $38.5 million ($2.82) in 1978. Revenues rose from $691.5 million to $834.5 million.

Also reporting earnings yesterday was Delta. Its earnings in the second quarter ended Dec. 31 were up to $34.1 million ($1.71 a share) from $33.5 million ($1.68). Revenues rose from $508.6 million to $574.2 million.

Because many of Delta's routes connect to Florida, its peak travel season begins late in the year, while most other airlines peak during the summer.

Delta's six-month results were also up, as earnings rose from $60.6 million ($3.05) to $66.8 millon ($3.36) and revenues increased from $973.7 million to $1.15 billion.

McDonnell-Douglas Corp. said fourth-quarter net income rose from $34.3 million (89 cens a share) in 1977 to $43.9 million (1.12) last year, while sales grew from $1.09 billion to $1.17 billion.

For the full year, net income was $161.1 million ($4.14) on sales of $4.13 billion compared with 1977 net income of $122.9 million ($3.20) on sales of $3.54 billion.

Inland Steel Co.'s 1978 fourth-quarter earnings were more than triple those of a year earlier, and full-year profits were nearly double 1977's, according to data released yesterday.

Inland, the nation's fifth largest steelmaker, said its fourth-quarter earnings were $47.6 million ($2.28 a share) compared with $15.7 million (74 cents) a year earlier. Sales rose from $672.6 million to $841.2 million.

Full-year earnings were $58.3 million ($7.61), up from $87.8 million ($4.23), and sales were $3.248 billion, up from $2.682 billion.

Wheeling-Pittsburgh Steel Corp reported 1978 net income of $19 million, the second highest annual income since a merger creating the company in 1968.

The earnings, amounting to $4.23 a share came on record annual sales of $1.1 billion. In 1977 -- a dismal year for steel in general -- the company lost $25.6 million on sales of $966 million.

The nation's ninth largest steel producer said fourth-quarter net income was $14.9 million ($3.76) on sales of $259.2 million. During the same period in 1977, Wheeling-Pittsburgh lost $4.9 million on sales of $239.1 million.

Shipments for 1978 totaled 2.9 million tons compared with 2.7 million tons in 1977.

Time Inc. said yesterday that strong increases in most of the giant publishing company's divisions offset losses from the Washington Star newspaper and the star-up costs of Life magazine and produced record annual sales and earnings.

Time also publishes Time, Fortune, Money, People and Sports Illustrated magazines and has extensive interests in paper production and cable television. It also is involved in book publishing and owns Book-of-the-month Club.

Net income rose to $119 million ($5.47 a share) in 1978 from $90.5 million ($4.44) in 1977. Revenues rose to $1.7 billion from $1.2k billion in 1977.

Fourth-quarter results were also healthy, with earnings rising to $37.1 million ($1.54) from $30.1 million ($1.51) a year ago. Sales were a$541.97 million, up from $367.48 million in 1977's fourth quarter.