2. Supplemental Balance Sheet Disclosures

Inventories

Inventories are stated at the lower of cost (first-in, first-out) or net realizable value, net of write-downs for excess and obsolete inventory, and consist of the following:


	March 31,		September 30,
	2021		2020

Raw materials	$	3,604,917	$	3,378,246
Work-in-process		778,151		656,382
Finished goods		271,043		256,707
	$	4,654,111	$	4,291,335

Prepaid expenses and other current assets

Prepaid expenses and other current assets consist of the following:


	March 31,		September 30,
	2021		2020

Prepaid insurance	$	551,379	$	336,331
Other		284,682		338,778
	$	836,061	$	675,109

Property and equipment

Property and equipment, net consists of the following:


	March 31,		September 30,
	2021		2020

Computer equipment	$	2,308,677	$	2,302,978
Corporate airplanes		5,601,039		5,601,039
Furniture and office equipment		970,725		1,031,099
Manufacturing facility		5,864,311		5,733,313
Equipment		5,553,890		5,723,355
Land		1,021,245		1,021,245
		21,319,887		21,413,029
Less: accumulated depreciation and amortization		(13,033,882)		(13,237,157)
	$	8,286,005	$	8,175,872

Depreciation and amortization related to property and equipment was approximately $95,844 and $97,610 for the three-month periods ended March 31, 2021 and 2020, respectively. The corporate airplanes are utilized primarily in support of product development. The Pilatus PC-12 airplane, one of the Company’s two corporate airplanes, has been depreciated to its estimated salvage value.

Depreciation and amortization related to property and equipment was approximately $188,895 and $194,254 for the six-month periods ended March 31, 2021 and 2020, respectively.

Other assets

Other assets consist of the following:


	March 31,		September 30,
	2021		2020
Intangible assets, net of accumulated amortization of $616,128 and $583,655 at March 31, 2021 and September 30, 2020, respectively	$	80,378	$	112,851
Operating lease right-of-use asset		5,637		45,126
Other non-current assets		88,456		91,566
	$	174,471	$	249,543

Intangible assets consist of licensing and certification rights which are amortized over a defined number of units. No impairment charges were recorded in the six-month periods ended March 31, 2021 and 2020.

Intangible asset amortization expense was approximately $12,559 and $0 for the three-month periods ended March 31, 2021 and 2020, respectively. Intangible asset amortization expense was approximately $32,473 and $4,800 for the six-month periods ended March 31, 2021 and 2020, respectively. The timing of future amortization expense is not determinable because the intangible assets are being amortized over a defined number of units.

Other non-current assets as of March 31, 2021 and September 30, 2020 include the security deposit for an airplane hangar and a deposit for medical claims required under the Company’s medical plan. In addition, other non-current assets as of March 31, 2021 and September 30, 2020 includes $13,156 and $16,266, respectively, of prepaid software licenses that will be earned upon the shipment of a certain product to a customer. Other non-current assets amortization expense was approximately $2,392 and $3,409 for the three- month periods ended March 31, 2021 and 2020, respectively. Other non-current assets amortization expense was approximately $3,110 and $6,100 for the six-month periods ended March 31, 2021 and 2020, respectively.

Accrued expenses

Accrued expenses consist of the following:


	March 31,		September 30,
	2021		2020

Warranty	$	579,011	$	547,743
Salary, benefits and payroll taxes		313,204		483,797
Professional fees		101,424		151,956
Operating lease		5,637		45,126
Other		259,734		133,338
	$	1,259,010	$	1,361,960

Warranty cost and accrual information for the three- and six-month periods ended March 31, 2021 is highlighted below:


	Three Months Ending		Six Months Ending
	March 31, 2021		March 31, 2021

Warranty accrual, beginning of period	$	578,172	$	547,743
Accrued expense		27,960		101,826
Warranty cost		(27,121)		(70,558)
Warranty accrual, end of period	$	579,011	$	579,011