Skymark
It looks as though Skymark management will have significant trouble completing all scheduled flights in April due to a "very critical shortage" of flight crews. Reasons for this shortage may be: minimum staffing/hiring practice, pilot attrition and limited training capacity.
Skymark Airlines operates 18 B747-800 aircraft to 13 destinations within Japan. They operate nearly 130 flights per day. Total number of qualified flight crew members is not definitive.