In fact our design business that accounts for approximately 90% of our profit, organic NSR, and backlog growth are at the top of the industry.
In addition, backlog in the design business increased by 8% and included 7% growth in contracted backlog, which is a leading indicator of revenue growth.
Our adjusted operating margin reached a new high this quarter at 14.1%, an increase of 90 basis points from the prior year.
As a result of this revenue and margin performance, adjusted EBITDA increased by 15% and adjusted earnings per share increased by 33%.
And consistent with our capital allocation policy, we repurchased approximately 12% of our shares outstanding as compared to last September when we began our repurchase program.
We delivered $3.7 billion of wins and we had a greater than one book to burn ratio for the enterprise for the first time since the pandemic began.
Today, we estimate approximately 70% of our revenue is directly related to ESG initiatives while nearly all of our revenue has at least some ESG element as a driver.
In Australia, the New South Wales government has advanced $130 billion package for four years of transportation spending.
Well, in Canada, there is more than $20 billion of public transit and green infrastructure spending.
And in Europe, the $1 trillion recovery fund requires 30% of spending to be dedicated to green and sustainable infrastructure.
This included our commitment to achieving Science based net carbon zero by 2030, expanding diversity and inclusion across our company and advancing the impact we can have on the world by embedding carbon reduction principles into our work to clients.
This is all part of the more than 1,000 digital practitioners we have across AECOM working to ensure we remain an innovator in our industry.
Compared to our fiscal 2018 margin, our third quarter segment adjusted operating margin of 14.1%, marks a 540 basis point improvement.
With increased delivery of higher margin work and our operational improvements, we expects to exceed our prior 13.2% margin guidance this year and we are confident in delivering our 15% by 2024 goal and longer term 17% aspirational target.
Total NSR declined slightly due to expected decline in Construction Management business, where we saw the deferral of a number of projects over the past 18 months.
Importantly, backlog in the Americas design business increased by 8%.
Adjusted operating margin was 18.9%, a 100 basis point increase from the prior year to a new high.
Our NSR increased by 7%.
Our adjusted operating margin in the third quarter was 7.3%, a 160 basis point improvement from the prior year and more than 500 basis point improvement since the beginning of fiscal 2019.
Our third quarter free cash flow of $295 million marked the highest level in four years, putting us on a strong path to achieving our full year guidance of between $425 million and $625 million.
Since September 2020, we have repurchased $930 million of stock, which represents nearly 19 million shares or 12% of our starting share balance.
With our year-to-date outperformance, we are raising our adjusted EBITDA guidance to between $810 million and $830 million or a 10% growth at the midpoint.
We are also increasing our adjusted earnings per share guidance for the full year to between $2.75 and $2.85 or 30% growth at the midpoint.
An extra week is approximately 7.5% of our quarterly NSR.

Summary:
Our NSR increased by 7%.