Air travel is responsible for 4% of warming to date[0], so an 80% growth would make aviation… responsible for 7.2% of current warming, or warming going up 3.2% compared to reality — sure, that's still bad, but it's not huge.

That said, if "80% of people aren't using aircraft" were true (I don't think it is), going from that to everyone wouldn't be "80% more air travel", it would be 400% more air travel, boosting global warming by 16%. Which is even worse, but again, not what I'd call "accelerate global warming hugely".

[0] more than you might expect from the 2.5% of global CO₂ emissions: https://ourworldindata.org/global-aviation-emissions