Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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Number of shares authorized for issuance under share-based payment arrangement.

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Gross number of share options (or share units) granted during the period.

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Aggregate value of stock related to Restricted Stock Awards issued during the period.

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Note 10 - Stock Options and Incentive Plans (Details Textual) - USD ($)			12 Months Ended
	Mar. 17, 2020	Apr. 12, 2019	Apr. 30, 2022	Apr. 30, 2021	Nov. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period (in shares)			50,000	50,000
Share-Based Payment Arrangement, Expense			$ 585,000	$ 592,000
Butler National Corporation 2016 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)					12,500,000
Stock Issued During Period, Value, Restricted Stock Award, Gross	$ 2,000,000.0	$ 950,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)		0
Butler National Corporation 2016 Equity Incentive Plan [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)	5,000,000.0	2,500,000
Share Price (in dollars per share)	$ 0.41	$ 0.38
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)		5 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period (in shares)			50,000	50,000
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total			$ 1,551
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)			3 years 6 months