What if the jettisoned objects were autonomous aircraft that could land accurately at a specified location?

A better idea would be to dig oil out of the ground, process it into kerosene, and use that to power jet turbines on the aircraft.

At some point we're going to need to stop doing that, hence the need for alternative ideas.

If the goal is to reduce carbon emissions from aviation then a more viable approach would be to produce liquid hydrocarbon fuel as a biofuel or through artificial synthesis using electrical power from renewable sources. Barring a technology breakthrough, batteries will only be usable for the shortest flights.

Sure. How about LNG (liquid methane)? We have enough natural gas to last quite a while. In the far future, hopefully we will have mastered producing kerosene using algae.

LNG tanks are far from lightweight; to keep LNG at room temperature is about 320 atmospheres of pressure. Liquid propane on the other hand is about 8 atmospheres. Mind you at altitude it's around -50 ~ -60 C, but that will only reduce the pressure requirements to approx 100 atm. Also, LNG has about 60% of the energy density of kerosene. SO to use LNG you'd be taking a double whammy, lower density and heavier tanks.

Sounds like propane is a winner. Would it help to use a composite tank a la SpaceX?