Note 11 - Industry Segmentation and Sales by Major Customer - Schedule of Segment Information by Products and Services (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2018	Apr. 30, 2017
Total revenues	$ 48,260	$ 50,619
Depreciation and amortization	1,760	1,985
Operating income	2,123	3,500
Capital expenditures, net	2,289	3,180
Interest expense	(331)	(403)
Other income (expense), net	4	(16)
Income before taxes	1,796	3,082
Income tax expense	540	768
Net income attributable to Butler National Corporation	341	1,534
Identifiable assets, net	41,431	42,778
Professional Services [Member]
Total revenues	31,283	30,849
Professional Services [Member] | Operating Segments [Member]
Total revenues	31,283	30,849
Depreciation and amortization	1,256	1,423
Operating income	1,721	1,622
Capital expenditures, net	631	2,296
Interest expense
Other income (expense), net
Income before taxes
Income tax expense
Net income attributable to Butler National Corporation
Identifiable assets, net	21,538	21,863
Aerospace Products [Member]
Total revenues	16,977	19,770
Aerospace Products [Member] | Operating Segments [Member]
Total revenues	16,977	19,770
Depreciation and amortization	504	562
Operating income	402	1,878
Capital expenditures, net	1,658	884
Interest expense
Other income (expense), net
Income before taxes
Income tax expense
Net income attributable to Butler National Corporation
Identifiable assets, net	$ 19,893	$ 20,915