Our orders were up 26% versus the same period last year, and we ended the first quarter with a backlog of 663 million.
Big oil companies are still cautious to invest even as oil is back above $60.
In order to meet customer demand, our team in Niella, Italy is in the process of executing several kaizens to increase our production by 30% with minimal capital investment.
Our first-quarter orders totaled $474 million, an increase of 26% compared to $375 million of orders in the same period last year.
On a currency-neutral basis, Q1 orders were up $78 million or 21%.
Our March 31 backlog of $663 million was better by 27% over the prior year and up 23% on a currency-neutral basis.
Backlog also increased across all of our segments with over 85% scheduled to ship within the next six months.
Compared to year-end, backlog was up 22% and, on a currency-neutral basis, up 25%.
Net sales in the first quarter of $354 million increased $25 million or 8% from a year ago.
Net sales were favorably impacted by 5% from changes in foreign currency exchange rates.
On an adjusted basis, SG&A expenses increased by approximately $1 million year over year.
Our adjusted EBITDA for the first quarter was $21 million, an increase of approximately 29% year over year.
As a percentage of sales, adjusted EBITDA margin improved to 6%, an improvement of 100 basis points over the prior year primarily due to leveraging of our fixed costs over a higher sales volume.
First-quarter depreciation of $10 million increased $1 million compared to the prior year, reflecting the higher level of capital expenditures in the second half of 2020.
In 2021, we anticipate total capital expenditures between $35 million and $40 million, which includes the investment in our European rental fleet.
Our GAAP diluted loss per share in the quarter was $0.09.
On an adjusted basis, diluted loss per share of $0.06 improved by $0.12 from the prior year, driven by increased operating income and partially offset by higher income tax expense.
We generated $41 million of cash from operating activities in the quarter compared to a use of $79 million in the prior year.
Capital spending in the quarter amounted to $8 million, of which $7 million related to the European tower rental fleet.
As a result, our free cash flow in the quarter was $34 million.
We ended the quarter with a cash balance of $159 million, an increase of $30 million from year-end.
Our total liquidity as of March 31 was $443 million with no borrowings on our ABL.
We expect to see costs for steel, logistics, and transportation increased as much as $30 million year over year.
With that, we are introducing full-year 2021 adjusted EBITDA guidance of $90 million to $105 million.
1, our European tower crane rental fleet strategy is on track.
During the first quarter, we invested approximately $7 million in capex on this initiative, with most of these cranes already rented and in service.
We plan to expand the fleet by another $8 million during the year.
2, our Chinese tower crane business continues to move forward.
We just launched a fourth new model designed by our China team, the Proton MCT 138.
More than 100 customers visit our factory for this product launch and the customer feedback was excellent.
3, in our altering crane business, we are investing an additional $4 million during 2021 in an effort to fill in product gaps.
Over the last three years, the main focus of our engineering team and the AT business was to improve our quality on legacy machines while updating designs to meet regulatory requirements, such as Tier 5 emission standards among a few others.
4, last but not least, we continue to pursue acquisition opportunities that will drive substantial long-term growth.

Summary:
Our GAAP diluted loss per share in the quarter was $0.09.
On an adjusted basis, diluted loss per share of $0.06 improved by $0.12 from the prior year, driven by increased operating income and partially offset by higher income tax expense.
With that, we are introducing full-year 2021 adjusted EBITDA guidance of $90 million to $105 million.