There is no jet fuel future with meaningful liquidity, so airlines hedge with heating-oil. There is no future on a specific corporate bond, so credit desks hedge with treasury-futures. There is no future on a single mid-cap stock, so a portfolio manager hedges with rty.
The trade-off is that the hedge only works to the extent the two prices move together. Correlation is estimated from history, applied through a hedge-ratio, and is at its weakest precisely when the market is stressed and the hedge is most needed.
Example: jet fuel and ULSD have moved together with a regression slope near 0.95. Hedging 1,000,000 gallons of jet requires 1,000,000 x 0.95 / 42,000 = 23 heating oil contracts, not 24 — and if the relationship slips to 0.80 in a refinery outage, roughly 15% of the exposure is uncovered.
Related: hedge-ratio, basis-risk, long-hedge, heating-oil, correlation