Consolidated Balance Sheets - USD ($) $ in Thousands	Apr. 30, 2021	Apr. 30, 2020
CURRENT ASSETS:
Cash	$ 22,022	$ 16,793
Accounts receivable, net of allowance for doubtful accounts	1,961	2,784
Inventories
Parts and raw materials	4,829	5,134
Work in process	3,657	3,419
Finished goods	82	62
Total inventory, net of allowance	8,568	8,615
Contract asset	421	195
Prepaid expenses and other current assets	1,496	1,620
Total current assets	34,468	30,007
PROPERTY, PLANT AND EQUIPMENT:
Lease right-to-use asset	3,099	44,349
Construction in progress	1,170
Land	4,751	1,809
Building and improvements	39,747	3,996
Aircraft	9,138	8,511
Machinery and equipment	4,253	4,093
Office furniture and fixtures	10,699	8,533
Leasehold improvements	4,032	4,032
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, before Accumulated Depreciation and Amortization	76,889	75,323
Accumulated depreciation	(20,519)	(20,577)
Total property, plant and equipment	56,370	54,746
SUPPLEMENTAL TYPE CERTIFICATES (net of accumulated amortization of $8,041 at April 30, 2021 and $7,029 at April 30, 2020)	8,211	6,483
OTHER ASSETS:
Other assets (net of accumulated amortization of $10,886 at April 30, 2021 and $10,153 at April 30, 2020)	2,872	3,546
Total other assets	2,872	3,546
Total assets	101,921	94,782
CURRENT LIABILITIES:
Current maturities of long-term debt	5,972	2,228
Current maturities of lease liability	107	1,163
Accounts payable	1,893	962
Contract liability	5,798	2,189
Gaming facility mandated payment	1,458	1,338
Compensation and compensated absences	1,862	2,571
Income tax payable	212	206
Other current liabilities	265	274
Total current liabilities	17,567	10,931
Long-term debt, net of current maturities	39,816	3,211
Lease liability, net of current maturities	2,759	42,211
Deferred tax liability	400	625
Total long-term liabilities	42,975	46,047
Total liabilities	60,542	56,978
COMMITMENTS AND CONTINGENCIES
STOCKHOLDERS' EQUITY:
Common stock, par value $.01: authorized 100,000,000 shares issued 79,070,382 shares, and outstanding 75,366,749 shares at April 30, 2021 and issued 77,719,677 shares, and outstanding 74,398,262 shares at April 30, 2020	790	777
Capital contributed in excess of par	16,900	15,600
Treasury stock at cost, 3,703,633 shares at April 30, 2021 and 3,321,415 shares at April 30, 2020	(1,909)	(1,713)
Retained earnings	19,580	18,147
Total Butler National Corporation's stockholders' equity	35,361	32,811
Noncontrolling interest in BHCMC, LLC	6,018	4,993
Total stockholders' equity	41,379	37,804
Total liabilities and stockholders' equity	101,921	94,782
Preferred Class A [Member]
STOCKHOLDERS' EQUITY:
Preferred stock
Preferred Class B [Member]
STOCKHOLDERS' EQUITY:
Preferred stock