To summarize, here are some of the reasons why we believe this: About 90% of our net sales are generated by proprietary products, and around three quarters of our net sales come from products for which we believe we are the sole source provider.
We raised an additional $1.5 billion at the beginning of our third quarter of fiscal-year '20.
We generated about $275 million of positive cash flow from operations and closed the quarter with almost $5 billion of cash.
We bought the Cobham Aero Connectivity business, which is an antenna and radio business, for a purchase price of $965 million.
Though we are not giving overall guidance for TransDigm, for the little less than nine months that we will own the Cobham business in fiscal '21, we expect it to contribute roughly $160 million in revenue with EBITDA as defined margins running in the 25% to 35% range.
We also sold two small nonproprietary former Esterline businesses that did not fit our model for about $30 million so far in 2021.
The total revenues for these businesses in fiscal-year '20 were roughly $35 million, and EBITDA was in the 10% revenue range.
Despite these headwinds, I am pleased that we were able to achieve a Q1 EBITDA as defined margin approaching 43%, which was a sequential improvement from our Q4 EBITDA as defined margin.
In the commercial market, which typically makes up close to 65% of our revenue, we split our discussion into OEM and aftermarket.
Our total commercial OEM market revenue declined approximately 40% in Q1 when compared with Q1 of the prior year period.
Total commercial aftermarket revenues declined by approximately 49% in Q1 when compared with Q1 of the prior year period.
On a positive note, the total commercial aftermarket revenues increased sequentially by approximately 5% when comparing the current quarter to Q4 fiscal 2020.
This is likely the result of destocking slowing at the airlines.
IATA's most recent forecast expects the final reported revenue passenger miles for calendar year 2020 to be 66% below 2019 and that calendar year 2021 average traffic levels will be about 50% of pre-COVID crisis levels.
Now let me speak about our defense market, which traditionally are at or below 35% of our total revenue.
The defense market, which includes both OEM and aftermarket revenues, grew by approximately 1% in Q1 when compared with the prior year period.
EBITDA as defined of about $474 million for Q1 was down 30% versus prior Q1.
EBITDA as defined margin in the quarter was just under 43%.
I am pleased that amid a disrupted commercial aerospace industry and in spite of the mix impact of low commercial aftermarket sales, we were able to expand our EBITDA as defined margin by approximately 40 basis points sequentially.
As Nick previously mentioned, we are not in a position to issue formal fiscal 2021 sales, EBITDA as defined and net income guidance at this time.
We assume a steady increase in commercial aftermarket revenue going forward and expect full year fiscal 2021 EBITDA margin roughly in the area of 44%, which could be higher or lower based on the rate of commercial aftermarket recovery.
For the quarter, organic growth was negative 24% driven by the commercial end market declines that Kevin mentioned.
That is, we still anticipate our GAAP cash and adjusted tax rates to all be in the 18% to 22% range.
Free cash flow, which we traditionally define at TransDigm as EBITDA as defined less cash interest payments, capex and cash taxes, was roughly $200 million.
We then saw an additional $70 million-plus come out of our net working capital driven by accounts receivable collections.
We ended the quarter with $4.9 billion of cash, up from $4.7 billion of cash at the end of last quarter.
There's one remaining piece of that acquisition, a Finland facility, representing 2% of the purchase price that's going through regulatory approvals now and should close soon.
Pro forma for the closing of this acquisition, our Q1 net debt-to-EBITDA ratio was a shade higher than 7.5 times Assuming air travel remains depressed, this ratio will continue ticking up through the end of Q2 of our fiscal 2021 when the last remaining pre-COVID quarter rolls out of the LTM EBITDA computation.

Summary:
This is likely the result of destocking slowing at the airlines.
As Nick previously mentioned, we are not in a position to issue formal fiscal 2021 sales, EBITDA as defined and net income guidance at this time.