It's very doable, but he's taking a huge risk that somebody else has $60 million to actually buy it.
If he ordered that plane on day 1, only putting down 20%, it would have cost about $7.5 million, leaving him 2.5 million to lease his 3 ATRs.
No way he earned enough profit to actually pay for the plane, but when a new plane is delivered and you don't have the cash for it, you still pay for it, and simply go into negative cash. you can't lease planes, do c-checks, etc at that point. B-checks might stop, too, not sure. His punctuality is very low, so he might have planes in poor condition, soon to be grounded. Marketing also stops, and combined with the poor punctuality, your CI will head down at high speed. But you don't get charged interest on the cash balance, your loans are frozen, rather than continuing to get bigger with interest, so as long as you've got enough profit to get back to 0 cash in a month or so, you'll survive.
He has a CV of 1.7 million. Roughly 5 million in loans and a 44 million asset would give a CV of 39 million. That means he has a negative cash balance of roughly 37 million. If someone buys his plane, he has 23 million in cash, and can begin to expand. If nobody buys his plane before c-checks are due, or his ATR leases need renewal, he'll lose those planes, and be in trouble. He can't afford to have the plane leased out, either, it won't provide that 30+ million cash quickly enough.
It's a novel strategy, for sure. And even if it sells now, and he instantly finds 8 a320s on the UM to spend his 23 million on, that just leaves him at 0 cash, -5 million CV, with 3 ATRs and 8 320s leased. Whereas someone else in his airport is over 20 planes already. Plus he'll be far behind in RI & CI, and have less slots available. And since the plane has been sitting there for over a month, and the biggest airlines ingame only have a 30 million CV, it's a strategy he'll probably be regretting.