Note 12 - Industry Segmentation and Sales by Major Customer - Schedule of Segment Information by Products and Services (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2018
Total revenues	$ 58,710	$ 48,260
Depreciation and amortization	1,846	1,760
Operating income	5,278	2,123
Capital expenditures, net	4,985	2,289
Interest expense	(248)	(331)
Refund of sales/use tax	1,995
Income before taxes	7,025	1,796
Income tax expense	1,375	540
Net income attributable to Butler National Corporation	3,853	341
Identifiable assets, net	48,902	41,431
Other income (expense), net		4
Professional Services [Member]
Total revenues	32,017	31,283
Professional Services [Member] | Operating Segments [Member]
Total revenues	32,017	31,283
Depreciation and amortization	1,068	1,256
Operating income	1,480	1,721
Capital expenditures, net	1,023	631
Interest expense
Refund of sales/use tax
Income before taxes
Income tax expense
Net income attributable to Butler National Corporation
Identifiable assets, net	22,432	21,538
Other income (expense), net
Aerospace Products [Member]
Total revenues	26,693	16,977
Aerospace Products [Member] | Operating Segments [Member]
Total revenues	26,693	16,977
Depreciation and amortization	778	504
Operating income	3,798	402
Capital expenditures, net	3,962	1,658
Interest expense
Refund of sales/use tax
Income before taxes
Income tax expense
Net income attributable to Butler National Corporation
Identifiable assets, net	$ 26,470	19,893
Other income (expense), net