Our recordable incident rate at the end of September was just 0.24 incidents per 200,000 labor hours, significantly better than industry averages.
Our trailing 12-month net cash from operations was $1.7 billion and free cash flow was $1 billion.
While there is always some uncertainty about the volume of ammonia that will be applied in Q4, given the dependency on weather, we would expect full year 2021 adjusted EBITDA to land between $2.2 billion and $2.4 billion.
On the balance sheet, we are quickly closing in on our target of $3 billion of gross debt and expect to repay the remaining $500 million outstanding on our 2023 notes on or before their maturity.
And as such, the Board has authorized a new $1.5 billion share repurchase program to facilitate the return of capital to shareholders.
Meanwhile, lower global production and government actions have created a supply constrained global market.
The impact of this can be seen on Slides 11 and 12, where both our spot cost curve and 2022 cost curve are much higher and steeper than in recent years.
For the first nine months of 2021, the company reported net earnings attributable to common stockholders of $212 million or $0.98 per diluted share.
EBITDA was $984 million and adjusted EBITDA was approximately $1.5 billion.
The trailing 12 months net cash provided by operating activities was approximately $1.7 billion and free cash flow was $1 billion.
In 2021, we completed a record level of maintenance activity that included turnarounds at seven of our 17 ammonia plants.
As a result, we expect to return to our typical high ammonia utilization rates, with gross ammonia production between 9.5 million and 10 million tons.
We expect to sell everything we produce and achieve sales volume between 19 million and 20 million tons in 2022.
As Tony said, our Board authorized the new $1.5 billion share repurchase program, which becomes effective January 1, 2022.
We continue to operate under our existing program, which has enabled us to acquire more than 11 million shares to be repurchased since 2019.
We expect the business to produce between $2.2 billion to $2.4 billion of adjusted EBITDA this year.

Summary:
Meanwhile, lower global production and government actions have created a supply constrained global market.
For the first nine months of 2021, the company reported net earnings attributable to common stockholders of $212 million or $0.98 per diluted share.