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, 2020	Apr. 30, 2019
Total revenues	$ 65,871	$ 58,710
Depreciation and amortization	5,116	1,846
Operating income	8,306	5,278
Capital expenditures, net	3,165	4,985
Interest expense	(4,368)	(248)
Gain on sale of airplanes	642
Income before taxes	4,580	7,025
Income tax expense	1,334	1,375
Net income attributable to Butler National Corporation	4,234	3,853
Identifiable assets, net	94,918	48,902
Other income (expense)		1,995
Professional Services [Member]
Total revenues	28,283	32,017
Professional Services [Member] | Operating Segments [Member]
Total revenues	28,283	32,017
Depreciation and amortization	3,740	1,068
Operating income	1,265	1,480
Capital expenditures, net	1,269	1,023
Interest expense
Gain on sale of airplanes
Income before taxes
Income tax expense
Net income attributable to Butler National Corporation
Identifiable assets, net	59,114	22,432
Other income (expense)
Aerospace Products [Member]
Total revenues	37,588	26,693
Aerospace Products [Member] | Operating Segments [Member]
Total revenues	37,588	26,693
Depreciation and amortization	1,376	778
Operating income	7,041	3,798
Capital expenditures, net	1,896	3,962
Interest expense
Gain on sale of airplanes
Income before taxes
Income tax expense
Net income attributable to Butler National Corporation
Identifiable assets, net	$ 35,804	26,470
Other income (expense)