The FINANCIAL -- The Boeing Company reported third-quarter revenue of $25.1 billion driven by higher defense volume and services growth. GAAP earnings per share increased to $4.07 and core earnings per share increased to $3.58 primarily driven by strong operating performance at Commercial Airplanes and a tax benefit related to a tax settlement ($0.71 per share).
Results also reflect charges related to planned investments in the newly awarded T-X Trainer and MQ-25 programs ($0.93 per share). Boeing delivered strong operating cash flow of $4.6 billion, repurchased $2.5 billion of shares, and paid $1.0 billion of dividends.
The company's revenue guidance increased $1.0 billion to between $98.0 and $100.0 billion, driven by defense volume and services growth, inclusive of the KLX acquisition. Operating cash flow guidance is reaffirmed at $15.0 to $15.5 billion. Full year GAAP earnings per share guidance is increased to between $16.90 and $17.10 from between $16.40 and $16.60 and core earnings per share (non-GAAP)* guidance is increased to between $14.90 and $15.10 from between $14.30 and $14.50 driven by a lower-than-expected tax rate and improved performance at Commercial Airplanes.
Operating cash flow in the quarter increased to $4.6 billion, primarily driven by timing of receipts and expenditures as well as planned higher commercial airplane production rates and strong operating performance. During the quarter, the company repurchased 7.0 million shares for $2.5 billion, leaving $9.6 billion remaining under the current repurchase authorization which is expected to be completed over approximately the next 12 to 18 months. The company also paid $1.0 billion in dividends in the quarter, reflecting a 20 percent increase in dividends per share compared to the same period of the prior year.
Cash and investments in marketable securities totaled $10.0 billion, compared to $9.8 billion at the beginning of the quarter. Debt was relatively stable at $11.9 billion.
Total company backlog at quarter-end was $491 billion, up from $488 billion at the beginning of the quarter, and included net orders for the quarter of $28 billion.
Commercial Airplanes third-quarter revenue of $15.3 billion was relatively unchanged, reflecting lower deliveries largely offset by mix. Third-quarter operating margin increased to 13.2 percent, reflecting higher 787 margin and strong operating performance on production programs, partially offset by $112 million of cost growth on the KC-46 Tanker program due to higher than expected effort to meet customer requirements to support delivery of the initial aircraft, as well as due to incremental delays in certification and testing.
During the quarter, Commercial Airplanes delivered 190 airplanes, including 57 737 MAX airplanes. The 777X program remains on track for delivery in 2020 as the static test airplane was completed and moved into test setup and the first two flight test airplanes were in production.
Commercial Airplanes booked 171 net orders during the quarter, valued at $13 billion. The 787 program has captured more than 100 orders in 2018 and nearly 1,400 orders since its launch. Backlog remains robust with more than 5,800 airplanes valued at $413 billion. Commercial Airplanes revenue guidance is reaffirmed at between $59.5 and $60.5 billion and margin guidance is increased to between 12% and 12.5% from greater than 11.5% on strong performance.
Defense, Space & Security third-quarter revenue increased to $5.7 billion driven by increased volume across government satellites, KC-46 Tanker, F/A-18 and weapons. Third-quarter operating margin was (4.3) percent, primarily reflecting $691 million of charges related to planned investments in the T-X and MQ-25 programs and $64 million related to cost growth on the KC-46 Tanker program.
During the quarter, Defense, Space & Security won key franchise program awards, including the T-X Trainer and MH-139 helicopter for the U.S. Air Force, the MQ-25 unmanned aircraft for the U.S. Navy, and the fourth KC-46 Tanker production lot. Significant milestones during the quarter included first flights of the Apache and Chinook for the Indian Air Force and receipt of Supplemental Type Certification for the KC-46 Tanker program, signifying completion of FAA certification. We also completed the acquisition of Millennium Space Systems, which will provide customers with advanced small-satellite technologies and flexible solutions.
Backlog at Defense, Space & Security was $58 billion, of which 31 percent represents orders from customers outside the U.S. Defense, Space & Security revenue guidance increased to between $22.5 and $23.0 billion from between $22.0 and $23.0 billion driven by higher volume and margin guidance is adjusted to greater than 6.5% from between 10% and 10.5% primarily to account for the investments in the business.
Global Services third-quarter revenue increased to $4.1 billion, primarily driven by higher parts volume (Table 6). Third-quarter operating margin was 13.3 percent reflecting mix and higher period costs.
During the quarter, Global Services was awarded P-8 training contracts for the U.S. Navy and Royal Australian Air Force, captured an order from GECAS for 20 737-800 converted freighters, and completed the first P-8A heavy maintenance check for the U.S. Navy. Global Services also secured contracts for F/A-18 spares for the Defense Logistics Agency and KC-46 Tanker services for Lots 3 and 4. In early October, Global Services completed the acquisition of KLX, which will enhance our services business and allow us to deliver greater value to customers.
Global Services revenue guidance increased to between $16.0 and $16.5 billion from between $15.5 and $16.0 billion driven by higher volume and margin guidance is reaffirmed at approximately 15.5%.
Additional Financial Information
At quarter-end, Boeing Capital's net portfolio balance was $3.1 billion. Revenue in other unallocated items and eliminations decreased primarily due to the 2017 sale of aircraft previously leased to customers. The change in earnings from other unallocated items and eliminations is primarily due to timing of expense allocations. The effective tax rate for the third quarter decreased from the same period in the prior year primarily due to a $412 million benefit related to a 2013-2014 tax settlement and the reduction of the federal tax rate to 21%.