Note 15 - Segment Reporting and Sales by Major Customer - Professional Services (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2021	Oct. 31, 2020	Oct. 31, 2021	Oct. 31, 2020
Revenues from customers	$ 19,093	$ 15,972	$ 37,237	$ 28,961
Interest expense	640	1,065	1,254	1,653
Depreciation and amortization	705	1,075	1,407	2,118
Operating income (loss)	4,743	1,687	8,765	1,815
Gaming [Member]
Revenues from customers	9,573	7,555	19,237	12,863
Interest expense	576	982	1,124	1,484
Depreciation and amortization	574	954	1,152	1,882
Operating income (loss)	3,075	1,621	6,619	1,011
Aircraft Modification [Member]
Revenues from customers	5,910	5,942	11,692	10,735
Interest expense	53	65	108	132
Depreciation and amortization	44	47	89	93
Operating income (loss)	1,245	471	2,388	1,387
Aircraft Avionics [Member]
Revenues from customers	665	625	1,540	1,539
Interest expense	0	0	0	0
Depreciation and amortization	1	1	3	3
Operating income (loss)	(114)	(98)	(133)	102
Special Mission Electronics [Member]
Revenues from customers	2,842	1,757	4,604	3,686
Interest expense	5	6	11	14
Depreciation and amortization	37	33	70	65
Operating income (loss)	1,485	520	1,988	1,119
Product and Service, Other [Member]
Revenues from customers	103	93	164	138
Interest expense	6	12	11	23
Depreciation and amortization	49	40	93	75
Operating income (loss)	$ (948)	$ (827)	$ (2,097)	$ (1,804)