As the world’s oxygen suddenly disappears and the population of Earth dies, a lone jet flies over the ocean – the last living people. Chaos spreads through the air-pressured cabin as the passengers come to grips with both their impending mortality and the end of humanity.

I agree with dpg. The air under the wings is what keeps the plane flying, without the air the plane crashes.

If you like the set up then change the location. Make it an underwater facility that loses it's oxygen tanks and the characters are slowly running out breathable air. (That's just an example)

The logline is problematical; it raises more questions than interest.

Is the whole atmosphere escaping into space, or just the oxygen? If the former, then the jet doesn't have the air its wings need to stay aloft.

CRASH!

And even if it's only the oxygen that is escaping, the jet engines won't have oxygen to burn the fuel to keep flying.

CRASH!

The logline is problematical; it raises more questions than interest.

Is the whole atmosphere escaping into space, or just the oxygen? If the former, then the jet doesn't have the air its wings need to stay aloft.

CRASH!

And even if it's only the oxygen that is escaping, the jet engines won't have oxygen to burn the fuel to keep flying.

CRASH!

But why are we invested in this lone jet?? If the world loses oxygen everyone must come to grips.... right? Who are the people on the plane, what makes us invested in them and not the whole entire universe?