Note 10 - Industry Segmentation and Sales by Major Customer - Schedule of Segment Information by Products and Services (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016
Net income attributable to Butler National Corporation	$ 1,534	$ 24
Identifiable assets, net	42,778	42,697
Total revenues	50,619	44,794
Depreciation and amortization	1,985	2,174
Operating income	3,500	622
Capital expenditures, net	3,180	2,757
Interest expense	(403)	(471)
Other income (expense), net	(16)	21
Income before taxes	3,082	908
Income tax expense	768	93
Professional Services [Member] | Operating Segments [Member]
Net income attributable to Butler National Corporation
Identifiable assets, net	21,863	22,462
Total revenues	30,849	29,784
Depreciation and amortization	1,423	1,390
Operating income	1,622	1,597
Capital expenditures, net	2,296	1,183
Interest expense
Other income (expense), net
Income before taxes
Income tax expense
Aerospace Products [Member] | Operating Segments [Member]
Net income attributable to Butler National Corporation
Identifiable assets, net	20,915	20,235
Total revenues	19,770	15,010
Depreciation and amortization	562	784
Operating income	1,878	(975)
Capital expenditures, net	884	1,574
Interest expense
Other income (expense), net
Income before taxes
Income tax expense