* Raises 2017 EPS forecast to $11.80-$12.10 from $11.30-$11.60
* Q1 sales $6.27 bln vs est $6.14 bln
* Shares down 1 pct (Adds details, background, shares, analyst's comment)
By Ankit Ajmera
April 26 (Reuters) - U.S. weapons maker Northrop Grumman Corp reported a higher-than-expected quarterly profit and revenue, helped by an increase in sales in its business that makes parts for F-35 fighter jets.
Sales in the aerospace unit, which also makes manned aircraft, drones and space craft, rose 12.6 percent to $2.90 billion, partly helped by higher F-35 deliveries.
The company's results come a day after larger rival Lockheed Martin Corp, the prime contractor for the F-35 program, also reported higher sales.
Helped by heightened geopolitical instability and a pro-defense outlook by U.S. President Donald Trump, defense stocks have surged in the past few months.
However, gains in shares of companies involved in the F-35 program, including Northrop and Lockheed, have been limited to some extent by Trump's criticism of the program as being too expensive.
The U.S. Defense Department expects to spend $391 billion in the coming decades to develop and buy 2,443 of the supersonic warplanes.
Northrop also raised its 2017 earnings forecast to $11.80-$12.10 per share from its previous forecast of $11.30-$11.60 due to a lower effective tax rate for the year.
Analysts on average had expected 2017 earnings of $11.87 per share, according to Thomson Reuters I/B/E/S.
Northrop's shares were down 1 percent at $246.50 in early trading on Wednesday.
The company's cash outflow for the first quarter was higher than the expectations of some analysts, while operating margin in its aerospace systems business fell to 10.8 percent from 11.1 percent a year earlier.
Northrop said sales in the aerospace business also benefited from its manned aircraft programs, including "restricted work".
The company won a contract in 2015 to produce the "Raider", the U.S. Air Force's new B-21 long-range bomber.
"We believe the B-21 could have accounted for $250 million of incremental revenues in the period (in the aerospace unit)," Jefferies analyst Howard Rubel wrote in a note to clients.
The estimated $80 billion program, expected to produce 100 aircraft, has been shrouded in secrecy since its inception.
Northrop's net earnings rose to $640 million, or $3.63 per share, in the quarter, from $556 million, or $3.03 per share, a year earlier. (bit.ly/2q6NHam)
Adjusted for pension costs, Northrop's earnings were $3.13 per share, compared with $2.77 a year earlier.
Total sales rose 5.2 percent to $6.27 billion.
Analysts on average had expected quarterly profit of $2.93 per share, on revenue $6.14 billion. (Reporting by Ankit Ajmera in Bengaluru and Mike Stone in Washington; Editing by Saumyadeb Chakrabarty)