As management looks at the company, we really believe that our success and the ability to keep our head well above water, not to get into any financial binds, not to struggle to sell debt at 8% or 10% and so forth and to be fiscally sound is all attributed to the unbelievable talent and brilliance of the team members.
Consolidated net sales for businesses that operate within the commercial aerospace industry decreased by about 43% in the first quarter of fiscal '21 as compared to the first quarter of fiscal '20.
And the cash flow provided by operating activities was very strong, increasing 32% to $107.2 million in the first quarter of fiscal '21, and that was up from $81.1 million in the first quarter of fiscal '20.
Operating income and net sales at flight support increased 20% and 3%, respectively, in the first quarter of fiscal '21 as compared to the fourth quarter of fiscal '20, clearly an improvement that's obvious.
Net sales for ETG, space and electronics products grew organically by a very strong 19% and 14%, respectively, in the first quarter of fiscal '21, while the ongoing pandemic's impact resulted in softer demand for its commercial aerospace products.
In January 21, we paid our regular semiannual cash dividend of $0.08 per share, and this represented our 85th consecutive semiannual cash dividend since 1979.
Total debt to shareholders' equity improved to 32.2% as of January 31, '21, and that compares to 36.8% as of October 31, '20.
Our net debt, which is total debt less cash and cash equivalents of $270.3 million as of January 31, '21, to shareholders' equity ratio improved to 13% as of January 31, '21.
And that was down from 16.6% as of October 31, '20.
Our net debt-to-EBITDA ratio improved to 0.62 times as of January 31, '21.
And that was down from 0.71 times on October 31, '20.
The Flight Support Group's net sales were $199.3 million in the first quarter of fiscal '21 as compared to $301.1 million in the first quarter of fiscal '20.
The Flight Support Group's operating income was $25.8 million in the first quarter of fiscal '21 as compared to $62 million in the first quarter of fiscal '20.
The Flight Support Group's operating margin was 13% in the first quarter of fiscal '21 as compared to 20.6% in the first quarter of fiscal '20.
The FSG operating margin was just 6.7% in the third quarter of fiscal '20 and has since steadily increased to 11.1% in the fourth quarter of fiscal 2020 and to 13% in the first quarter of fiscal '21.
But HEICO demonstrates it through actions, including by maintaining our 401(k) matching contributions and granting our team members their maximum potential 401(k) profit sharing contributions, even though we missed our budgets due to the pandemic.
About 90% of our people cannot work from home and have to come in.
As for the Electronic Technologies Group's performance, our net sales increased 7% to $223.6 million in the first quarter of fiscal '21, up from $208.4 million in the first quarter of fiscal '20.
The Electronic Technologies Group's operating income increased 5% to $60.1 million in the first quarter of fiscal '21, up from $57.5 million in the first quarter of fiscal '20.
The Electronic Technologies Group's operating margin was 26.9% in the first quarter of fiscal '21 as compared to 27.6% in the first quarter of fiscal '20.
Consolidated net income per diluted share was $0.51 in the first quarter of fiscal '21 and that compared to $0.89 in the first quarter of fiscal '20.
Depreciation and amortization expense totaled $23 million in the first quarter of '21.
That was up from $21.6 million in the first quarter of fiscal '20.
R&D expense was $16.2 million in the first quarter of fiscal '21 or about 3.9% of sales, and that compared to $17.1 million in the first quarter of fiscal '20 or 3.4% of sales.
Consolidated SG&A expense decreased by 10% to $78.1 million in the first quarter of fiscal '21 as compared to $87.1 million in the first quarter of fiscal '20.
Consolidated SG&A expense as a percentage of net sales was 18.7% in the first quarter of fiscal '21, and that compared to 17.2% in the first quarter of fiscal '20.
Interest expense decreased to $2.4 million in the first quarter of fiscal '21, and that was down from $4.3 million in the first quarter of fiscal '20.
HEICO's income tax expense was $2.3 million in the first quarter of fiscal '21, and that compared to an income tax benefit of $22.9 million in the first quarter of fiscal '20.
HEICO recognized a discrete tax benefit from stock option exercises in both the first quarter of fiscal '21 and '20 of $13.5 million and $47.6 million, respectively.
The tax benefit from stock option exercises in both periods was the result of the strong appreciation in HEICO's stock price during the option lease holding period, and the $34.1 million larger benefit recognized in the first quarter of fiscal '20 was the result of more stock options which were exercised.
Net income attributable to noncontrolling interest was $5.7 million in the first quarter of fiscal '21, and that compared to $7.9 million in the first quarter of fiscal '20.
For the full FY '21, we now estimate a combined effective tax rate and noncontrolling interest rate of approximately 24% to 26% of pre-tax income.
As we mentioned earlier, cash flow provided by operating activities was very strong and increased 32% to $107.2 million in the first quarter of fiscal '21, up from $81.1 million in the first quarter of fiscal '20.
Our working capital ratio was strong and consistent at 4.9 times as of January 31, '21, and that compared to 4.8 as of October 31, '20.
Days sales outstanding of receivables, DSOs, improved to 45 days as of January 31, '21, and that compared to 46 days as of January 31, '20.
No one customer accounted for more than 10% of net sales.
Our top five customers represented about 24% and 22% of consolidated net sales in the first quarter of fiscal '21 and '20, respectively.
Our inventory turnover rate increased to 164 days for the period ending January 31, '21.
That compared to a pre pandemic 132 days for the period ended January 31, '20.
And in consideration of HEICO's consolidated backlog, which has increased by $62 million since October 31, '20, the backlog was $906 million as of January 31, '21.
Given this uncertainty, we cannot provide fiscal '21 net sales and earnings guidance at this time.
And again, this year, we continue to make the 5% match to team members' 401(k) investments.
As you know, most team members invest 6%, HEICO matches it with 5% of their salary in HEICO shares.

Summary:
And the cash flow provided by operating activities was very strong, increasing 32% to $107.2 million in the first quarter of fiscal '21, and that was up from $81.1 million in the first quarter of fiscal '20.
Consolidated net income per diluted share was $0.51 in the first quarter of fiscal '21 and that compared to $0.89 in the first quarter of fiscal '20.
As we mentioned earlier, cash flow provided by operating activities was very strong and increased 32% to $107.2 million in the first quarter of fiscal '21, up from $81.1 million in the first quarter of fiscal '20.
Given this uncertainty, we cannot provide fiscal '21 net sales and earnings guidance at this time.