You are given a text that consists of multiple sentences. Your task is to perform abstractive summarization on this text. Use your understanding of the content to express the main ideas and crucial details in a shorter, coherent, and natural sounding text. 
Text: These estimates are subject to some risks and uncertainties.
Additional information regarding these factors is contained in the company's 10-K, 10-Q and 8-K filings.
Revenue is up $640 million or 7.3% against the first quarter last year.
Operating earnings are up $4 million, and net earnings are up $2 million.
To be a little more granular, revenue on the defense side of the business is up against last year's first quarter by $444 million, and aerospace is up $196 million.
The operating earnings on the defense side are up $45 million or 6.4%, while operating earnings in the aerospace side are down $20 million, but still nicely above consensus.
I will have more to say about this a bit later.
The operating margin for the entire company was 10%, 70 basis points lower than the year-ago quarter.
This was driven by a 250-basis-point lower margin rate at aerospace, as was fully anticipated in our guidance to you, combined with $21 million more in corporate operating expense.
From a slightly different perspective, we beat consensus by $0.18 per share.
We have roughly $500 million more in revenue than anticipated by the sell side and almost $50 million more in operating earnings.
So it's a pure operations beat.
I must confess that we also beat our own expectations rather handsomely.
This is, in almost all respects, a very solid quarter.
It's hard to find something not to like about it.
It's a very good start to the year.
Aerospace enjoyed revenue of $1.9 billion and operating earnings of $220 million with an 11.7% operating margin.
Revenue is almost $200 million higher than anticipated by us and the sell side.
Revenue is also $196 million higher than the year-ago quarter.
The difference is almost exclusively more G500 and G600 deliveries than the year-ago quarter.
The 11.7% operating margin is lower than the year-ago quarter, but consistent with our guidance and sell-side expectations.
Finally, we took some mark-to-market charges with respect to our G500 test inventory.
Without the charge, from a pure operating perspective, performance in the quarter was superb.
Aerospace also had a very strong quarter from an orders perspective with a book-to-bill of 1.3:1.
Gulfstream alone had a book-to-bill of 1.34:1.
In unit terms, this is the strongest order quarter for the last two years, excluding the fourth quarter of 2019 when we launched the G700.
The sales activity truly accelerated in the middle of February and continued on through the remainder of the quarter.
The momentum developed in the quarter appears to be rolling over into the second quarter as well.
We are experiencing a high level of interest and activity.
It is constructive to see this accelerated activity level without the benefit of the removal of travel restrictions and quarantine requirements in many countries outside the U.S. Demand should improve even further when these restrictions are ultimately removed.
Gulfstream experienced a 5.7% increase in service revenue.
On the other hand, Jet Aviation's FBOs and certain of its maintenance facilities are recovering more slowly.
Jet Aviation service revenue is down around $31 million, coupled with a modest increase in service operating earnings.
The FBOs and MRO sites will do much better as business travel accelerate.
The G500 and G600 continued to perform well.
Margins are improving on a consistent basis, and quality is superb.
As of the end of last week, we have delivered 104 of these aircraft to customers.
The G700 has over 1,400 test hours on the five test aircraft, and the first fully outfitted G700 is flying.
Its interior is absolutely beautiful.
We remain on track for entry into service in the fourth quarter of 2022.
Looking forward, we expect the second quarter to be our most challenging from a delivery perspective.
However, we also expect rapid improvement in the third and fourth quarters as we had planned for an increase in production and more delivery.
Combat systems has revenue of $1.8 billion, up 6.6% over the year-ago quarter.
While all three companies within the group contributed to the growth, the primary source was increased sales of our eight by eight-wheeled combat vehicles to Switzerland and Spain and sales of our six by six Eagle vehicles.
So all in all, good growth.
It is also interesting to observe that combat systems revenue has grown in 16 of the last 18 quarters on a quarter over the year-ago quarter basis.
Operating earnings, at $244 million, are up 9.4% on higher volume and a 30-basis-point improvement in margin.
This was an impressive performance by any reasonable measure.
You may recall that a notable development for this segment in the year-ago quarter was the formal signing of the restructured contract on the Canadian international program, which settled all issues.
The parties continue to perform on that contract, as contemplated.
This was helpful to free cash flow last year and continues to be so this year.
This risk item appears to be behind us.
Turning to marine systems.
You may recall that at this time a year ago, I was able to report that revenue in the first quarter of 2020 was up 9.1% against the first quarter in 2019.
I am very pleased to report today that first-quarter 2021 revenue of $2.48 billion is up 10.6% against first-quarter 2020.
The growth was led by Block V Virginia-class and Columbia-class construction volume.
We also enjoyed nice increases in ESB and T-AO construction volume at NASSCO.
This is very impressive continued growth.
In fact, revenue in this group has been up for the last 14 quarters on a quarter versus the year-ago quarter basis.
Operating earnings are $200 million in the quarter, up $16 million or 8.7% on an operating margin of 8.1%.
We will strive to improve our operating margin as we progress through the year.
On the order side, I should observe that total backlog was down only $231 million sequentially, leaving a powerful $49.8 billion in total backlog.
There was, obviously, significant order activity in the quarter, including the award of the 10th Block V Virginia-class submarine.
This segment have revenue of almost $3.2 billion in the quarter, up $95 million from the year-ago quarter or 3.1%.
The revenue increase was supplied by information technology, mostly associated with the ramp-up of new programs.
IT alone grew 5% in the quarter.
Operating earnings at $306 million or up $8 million or 2.7% on a 9.6% operating margin.
This is about 40 basis points ahead of consensus.
EBITDA margin is an impressive 13.3%, including state and local taxes, which are a 50-basis-point drag on that result.
Most of our competitors carry state and local taxes below the line.
This is a best-in-class EBITDA margin.
Total backlog grew $359 million sequentially, and total estimated contract value remained about the same.
There were also some notable items in GDIT's first quarter worth mentioning.
On the bid and proposal front, GDIT submitted the highest dollar value of proposals in any quarter since the acquisition of CSRA, 90% of which represent new business opportunities.
They ended the quarter with over $30 billion in proposals awaiting customer decision, most of which also represent new business opportunities versus recompetition of existing work.
So good order activity in the quarter with a book-to-bill of 1.1:1 and good order prospects on the horizon.
That concludes my remarks with respect to a very good quarter.
As you know, we never update guidance at this time of the year.
We will, however, give you a comprehensive update at the end of the second quarter, as is our custom.
I'll start with our cash performance in the quarter.
From an operating cash flow perspective, we essentially broke even for the quarter.
Including capital expenditures, our free cash flow was negative $131 million.
For those of you who followed us for some time, you know we've been a fairly significant user of cash in the first quarter for the past several years.
This quarter was a marked improvement from that pattern due in large part to the strong order activity at Gulfstream and ongoing progress payments on our large international combat systems program, consistent with the contract amendment Phebe referenced earlier.
So the quarter was nicely ahead of our expectations and reinforces our outlook for the year of free cash flow conversion in the 95% to 100% range.
Looking at capital deployment, I mentioned capital expenditures, which were $134 million in the quarter or 1.4% of sales.
That's down between 25% and 30% from the first quarter a year ago, but we're still expecting full-year capex to be roughly 2.5% of sales.
We also paid $315 million in dividends and increased the quarterly dividend by a little more than 8% to $1.19 per share.
And we spent nearly $750 million on the repurchase of 4.6 million shares at an average price of just over $161 per share.
After all this, we ended the first quarter with a cash balance of $1.8 billion and a net debt position of $11.4 billion, down $1.3 billion from this time last year.
Net interest expense in the quarter was $123 million, up from $107 million in the first quarter of 2020.
The increase in 2021 is due to the incremental debt issued last year in conjunction with the refinancing of maturing notes.
We have $3 billion of outstanding debt maturing later this year, and we plan to refinance a portion of those notes to achieve a more balanced deployment of capital, but this will still result in a declining debt balance this year and beyond.
During the quarter, Congress passed the American Rescue Plan Act.
As you may be aware, it contains two provisions that affect our business.
First, it extends the provision of the CARES Act that allows reimbursement of contractor payments to workers who are prevented from working due to COVID-related facility closures.
This will continue to benefit our technologies business, although it does not provide for fee on those costs.
So that will have an ongoing dilutive impact on the segment's margins.
Second, the act provides pension funding relief by reducing the amount of required contribution to our pension plans this year by a couple of hundred million dollars.
However, this same provision reduces the amount of pension costs we are reimbursed on our U.S. government contracts.
As a result, when coupled with the lower tax benefit from the reduced pension contributions, the impact on our 2021 cash flow is immaterial.
We expect the cash benefit from the act to increase modestly over the next couple of years, reinforcing our expectation that free cash flow can exceed 100% of net income over that period.
The tax rate in the quarter, at 16.2%, is consistent with our full-year expectation, so no change to our outlook on that front.
Finally, order activity and backlog were once again a strong story in the first quarter with a 1:1 book-to-bill for the company as a whole, even as we grew by more than 7% in the quarter.
As Phebe mentioned, the order activity in the aerospace and technologies groups led the way with a 1.3 times and 1.1 times book-to-bill, respectively.
We finished the quarter with a total backlog of $89.6 billion.
That's up 4.5% over this time last year.
And total potential contract value, including options and IDIQ contracts, was $131.4 billion, up 6% over the year-ago quarter.
Howard, that concludes my remarks.
As a reminder, we asked participants to ask one question and one follow-up, so that everyone has chance to participate.
Operator, could you please remind participants how to enter the queue?

user
q1 earnings per share $2.48.
q1 revenue rose 7.3 percent to $9.4 billion.
total backlog at end of first-quarter 2021 was $89.6 billion, up 4.5% from year-ago quarter.
total estimated contract value, sum of all backlog components, was $131.4 billion at end of quarter.

assistant