Lump sum would help
If a retirement plan is properly funded, a lump-sum option shouldn't incur any actuarial cost; the payout is offset by reduced future obligations. But many plans are not fully funded, and use wildly optimistic projections for growth of the fund's investments. This makes the company's books look better in the short term, and is why a lump-sum option will be resisted. Too bad, because many senior pilots would take it if they could, greatly easing the SLI problem.