Linde plc has reported third-quarter 2021 income from continuing operations of $978 million and diluted earnings per share of $1.88, an increase of 42% versus prior year. Excluding Linde AG purchase accounting impacts and other charges, adjusted income from continuing operations was $1,421 million, up 25% versus prior year and flat sequentially. Adjusted earnings per share was $2.73, 27% above prior year and 1% higher sequentially.
Linde's sales for the third quarter were $7,668 million, 12% above prior year and up 1% sequentially. Compared to prior year, underlying sales increased 11%, including 3% price attainment and 8% higher volumes. Volume growth was broad-based across all geographic segments and end markets. Sequentially, underlying sales increased 1% driven by higher price.
Third-quarter operating profit was $1,292 million. Adjusted operating profit of $1,810 million was up 19% versus prior year led by higher price, strong volumes and continued productivity initiatives across all segments. Adjusted operating margin of 23.6% expanded 150 basis points versus prior year and 220 basis points when excluding the effects of cost pass-through. Sequentially, operating margins were stable when excluding cost pass-through. Cost pass-through represents the contractual billing of energy cost variance, primarily to onsite customers, with minimal effect on profit.
Third-quarter operating cash flow of $2,556 million increased 36% versus prior year and 40% sequentially. After capital expenditures of $741 million, free cash flow was $1,815 million, up 65% versus prior year and 68% sequentially. During the quarter, the company returned $1,708 million to shareholders through dividends and stock repurchases, net of issuance.
In addition, the company ended the third quarter with a total backlog of approximately $13.4 billion which includes both sale of gas and sale of plant projects, all contractually secured with high-quality customers.
Commenting on the financial results and business outlook, Chief Executive Officer Steve Angel said, "Linde employees delivered another stellar quarter achieving record EPS, operating cash flow and return on capital. We maintained our industry leading performance and significantly expanded our project backlog. We also announced new GHG emission goals including a commitment to absolute emissions reduction, reaching climate neutrality by 2050."
Angel continued, "The Linde team demonstrated, once again, they can deliver in any environment. We are well positioned for the future and I am confident our best days, indeed, lie ahead."
For full year 2021, the company has updated its adjusted diluted earnings per share guidance to be in the range of $10.52 to $10.62, up 43% to 45% versus 2019 and 28% to 29% versus prior year. This guidance assumes 3% currency tailwind versus 2020. Full-year capital expenditures are expected to be in the range of $3.0 billion to $3.2 billion to support maintenance and growth requirements including the contractual project backlog.
