Consolidated Balance Sheets - USD ($) $ in Thousands	Apr. 30, 2018	Apr. 30, 2017
CURRENT ASSETS:
Cash	$ 7,353	$ 6,389
Accounts receivable, net of allowance for doubtful accounts	3,107	4,095
Income tax receivable	219
Inventories
Parts and raw materials	5,858	5,644
Work in process	1,234	1,174
Finished goods	27	39
Total inventory, net of allowance	7,119	6,857
Prepaid expenses and other current assets	978	994
Total current assets	18,776	18,335
PROPERTY, PLANT AND EQUIPMENT:
Land and building	5,232	5,132
Aircraft	6,157	5,888
Machinery and equipment	3,922	3,639
Office furniture and fixtures	6,658	6,497
Leasehold improvements	4,032	4,032
	26,001	25,188
Accumulated depreciation	(15,725)	(14,506)
Total property, plant and equipment	10,276	10,682
SUPPLEMENTAL TYPE CERTIFICATES (net of accumulated amortization of $5,164 at April 30, 2018 and $4,345 at April 30, 2017)	6,597	6,354
OTHER ASSETS:
Deferred tax asset	193	925
Other assets (net of accumulated amortization of $8,213 at April 30, 2018 and $6,904 at April 30, 2017)	5,589	6,482
Total other assets	5,782	7,407
Total assets	41,431	42,778
CURRENT LIABILITIES:
Promissory notes	2,387	2,604
Current maturities of long-term debt	1,612	2,297
Accounts payable	2,215	1,919
Customer deposits	1,396	892
Gaming facility mandated payment	1,219	1,227
Compensation and compensated absences	1,439	1,478
Income tax payable		589
Other current liabilities	162	129
Total current liabilities	10,430	11,135
LONG-TERM DEBT, NET OF CURRENT MATURITIES:	1,735	3,347
Total liabilities	12,165	14,482
COMMITMENTS AND CONTINGENCIES
STOCKHOLDERS' EQUITY:
Common stock, par value $.01: authorized 100,000,000 shares issued 66,196,854 shares, and outstanding 64,743,317 shares at April 30, 2018 and issued 65,273,896 shares, and outstanding 64,543,550 shares at April 30, 2017	662	652
Capital contributed in excess of par	14,231	13,980
Treasury stock at cost, 1,453,537 shares at April 30, 2018 and 730,346 shares at April 30, 2017	(951)	(764)
Retained earnings	10,060	9,719
Total Butler National Corporation's stockholders' equity	24,002	23,587
Noncontrolling interest in BHCMC, LLC	5,264	4,709
Total stockholders' equity	29,266	28,296
Total liabilities and stockholders' equity	41,431	42,778
Preferred Class A [Member]
STOCKHOLDERS' EQUITY:
Preferred stock
Preferred Class B [Member]
STOCKHOLDERS' EQUITY:
Preferred stock