Note 1 - Nature of Operations, Organization and Significant Accounting Policies - Supplemental Type Certificates Capitalized Costs (Details) - USD ($)	Apr. 30, 2019	Apr. 30, 2018
Direct labor	$ 2,670,000	$ 2,494,000
Direct materials	3,345,000	3,099,000
Consultant costs	1,922,000	1,922,000
Overhead	4,524,000	4,246,000
	12,461,000	11,761,000
Supplemental type certificates, accumulated amortization	6,054,000	5,164,000
STC balance	$ 6,407,000	$ 6,597,000