Flying $450 million airliners was once a dream job, and there was no shortage of opportunity. Last year Boeing Co. estimated that airlines would need to add 800,000 pilots over the next 20 years to feed an Asia-led travel boom; some carriers in China were offering salaries of more than $300,000 a year, plus perks, to woo industry veterans.

Then coronavirus began to spread and overseas travel halted, grounding 51% of the world’s global fleet. As they wait to see whether they’ll ever get back in the cockpit, pilots have turned to a mishmash of odd jobs and second-choice careers…